Sexual behaviours among MSM during the first COVID-19 lockdown not associated with risk of COVID-19 infection

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Schori, Olivia J. Kotoun, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4169289/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 02 Nov, 2024 Read the published version in BMC Public Health → Version 1 posted 10 You are reading this latest preprint version Abstract Background: The social distancing measures associated with the COVID-19 pandemic had far reaching effects on sexual behavior worldwide. However, it remains unclear whether sexual contact with non-steady partners was a contributor to the spread of SARS-CoV-2. The aim of this study was to (i) assess whether the SARS-CoV-2 seropositivity after the first pandemic wave among people using HIV Pre-Exposure Prophylaxis (PrEP) in Zurich, Switzerland differed from that of a demographic matched population level comparison group, (ii) describe risk factors for SARS-CoV-2 seropositivity in this population, and (iii) determine whether sexual contact with non-steady partners was associated with SARS-CoV-2 seropositivity. Methods: The study was conducted between July 2020 and October 2020 as a nested cross-sectional study within two ongoing cohort studies, SwissPrEPared (all eligible PrEP users in Switzerland ≥18 years old) and Corona Immunitas (a series of cross-sectional and longitudinal studies measuring the SARS-CoV-2 seroprevalence across Switzerland, beginning in April 2020). All SwissPrEPared participants were recruited from Checkpoint Zurich (the main PrEP clinic in Zurich). Data were collected on participants’ SARS-CoV-2 antibody status, social characteristics and behavioral data after the first wave of the corona pandemic in Switzerland, and seroprevalence was compared with a propensity score-matched sample from the general Zurich population. Results: Of the 218 participants enrolled, 8.7% (n=19, 95% CI: 5.5-13.5%) were seropositive for SARS-CoV-2 during the first pandemic wave, higher than that of the general male population in Zurich aged 20-65 (5.5%, 95% CI: 3.8–8.2%). Participants on average reduced their social outings, but the seronegative were more socially active before, during, and after the first lockdown period. In a logistic model, increasing mean sexual partner count was not associated with seropositivity (OR: 0.9, 95% CI: 0.8, 1.0), but increasing number of trips abroad was associated with higher seropositivity (p=0.06, OR: 1.14, 95% CI: 1.0, 1.3). The estimated risk ratio for seropositivity for the participants compared to the general Zurich population after propensity score matching was 1.5 (95% CI: 0.53, 4.0). 94% of participants reported later receiving a COVID-19 vaccination. Discussion: Our study suggests that COVID-19 seropositivity was slightly elevated among people taking PrEP in Zurich during the first wave of the pandemic, but that socializing and sexual activity were less important than other factors in contributing to risk. Figures Figure 1 Figure 2 Background Soon after the emergence of SARS-CoV-2, unprecedented restrictions on social contact and mobility were implemented globally to contain the virus, including rules on restricting sexual contacts. These restrictions often had unintended consequences, especially on mental health, 1 stress, substance use, and sleep patterns. 2–4 These consequences were not evenly distributed among the population, with the burden of the mental health effects of social distancing falling disproportionately on vulnerable populations such as adolescents, young people, and people with minority sexual orientation or gender identity. 4–6 In Switzerland, social distancing measures were implemented starting in March 2020, and the strongest restrictions occurred over the first waves of the pandemic. Social distancing measures were particularly difficult for people with non-steady sexual partners to implement. 6 Sexual behavior is complex and cannot be changed easily; previous research has shown that mate-seeking motives (especially among young men) was one of the strongest predictors of lack of compliance with social distancing measures. 7 People who are not in steady sexual relationships are more likely to live alone and thus more likely to suffer from social and mental isolation due to the restrictions. A study in Germany showed that loneliness, anxiety and depression during the pandemic were particularly high among people with minority sexual orientation or gender identity, and especially those living alone. 5 Some estimates suggest that over 50% of urban households are solitary in many metropolitan areas, 2 and that men having sex with men (MSM) are particularly likely to live alone. 6 A robust scientific evidence base has emerged that the first phases of the COVID-19 pandemic had significant effects on sexual behavior worldwide. 6,8 However, few studies focused specifically on people with non-steady sexual partners or the result of changes in their sexual behavior on risk of acquiring SARS-CoV-2. 8 Much of the research in this area has focused on MSM, partly due to pre-existing research on sex behaviors in this population. Most studies on changes in sexual activity among MSM showed reductions in numbers of sexual partners during the first phases of the pandemic. 1,9–12 However, a few studies showed no change or even increases in the number of sexual partners in this population during the first year of the pandemic. 13–15 It still remains poorly understood how social distancing measures during the pandemic affected the sexual health of people not in a steady relationship. It also remains unclear whether sexual contact with non-steady partners was a contributor to the spread of SARS-CoV-2. As HIV PrEP-exposure prophylaxis (PrEP) is almost exclusively taken by people with multiple sexual partners, some studies have taken advantage of existing PrEP cohorts to investigate how the pandemic investigated sexual risk taking. 1,16–20 However, these studies suffered from lack of a comparable population cohort to understand whether risk was elevated in PrEP cohorts compared to other populations with similar demographic characteristics. In our study, we were able to integrate people taking PrEP into an existing population level seroprevalence study (Corona Immunitas) to better examine and compare the influence of sexual behavior on the COVID-19 pandemic on this population. The aim of this study was to (i) assess whether the SARS-CoV-2 seropositivity after the first pandemic wave among people using PrEP in Zurich differed from that of a demographic matched population level comparison group, (ii) describe risk factors for SARS-CoV-2 seropositivity in this population, and (iii) determine whether sexual contact with non-steady partners was associated with SARS-CoV-2 seropositivity. Methods Study design, setting and participants This study is a cross-sectional study nested within two ongoing studies: SwissPrEPared and Corona Immunitas. The study was conducted between July 2020 and October 2020, a period corresponding to the end of the first pandemic wave and the beginning of the second. SwissPrEPared national program and cohort study The SwissPrEPared program is a large, ongoing nation-wide Swiss cohort of PrEP users. Individuals are eligible to participate if they are ≥18 years old and express interest in PrEP in one of the participating medical centers. The enrollment for the SwissPrEPared study is detailed elsewhere, 21 but in brief, all persons interested in PrEP and 18 years of age or older living in Switzerland are eligible for the SwissPrEPared study. Following international recommendations, three monthly screenings for counseling and STI screening are recommended for those on daily PrEP and at least six monthly screenings for those on event-based PrEP. Active participants of the SwissPrEPared study who attended Checkpoint Zurich for their routine PrEP appointments between July 15 and October 6, 2020 (before the second wave of the COVID-19 pandemic hit Switzerland), were eligible for participation in the Corona Immunitas substudy. Checkpoint Zurich is the largest PrEP center in Switzerland. Corona Immunitas national research program Corona Immunitas is a nation-wide Swiss research program of cross-sectional and longitudinal SARS-CoV-2 seroprevalence studies that investigated the spread and impact of infection with SARS-Cov-2 in Switzerland over six phases (https://www.corona-immunitas.ch/en/). 22–26 To ensure comparability, a standardized protocol (ISRCTN18181860) 27 including the same baseline questionnaire and serological testing was administered in the Swiss general population and in several subpopulations. 28 For this study, we used data from Corona Immunitas phase 2 of the canton of Zurich, for which randomly selected individuals from the general population were recruited using age stratified sampling (20-64 years, ≥65 years) and invited to participate. The SwissPrEPared study (NCT03893188) was approved by the lead ethical committee (EC) in Zurich on 14 May 2019 (BASEC Nr. 2018-02015), followed by the approval of all ECs from the other cantons. The Corona Imunitas study was approved by the lead EC in Zurich (BASEC Nr. 2020-01247), followed by the approval of all ECs from the other cantons. All participants signed a written informed consent. Procedures and measurements A poster with information about the Corona Immunitas study and the study team contact information was placed in the Checkpoint Zurich waiting area. During their routine visits, SwissPrEPared participants were informed about the Corona Immunitas study by their healthcare providers, and given contact information for the study team. Finally, all Checkpoint Zurich SwissPrEPared participants who were not yet enrolled in Corona Immunitas were sent a text message inviting them to enroll. The Corona Immunitas study team contacted all participants by email or telephone, answered questions, arranged an enrollment visit, and sent out an electronic version of the informed consent and Corona Immunitas standardized baseline questionnaire prior to the enrollment visit. The Corona Immunitas standardized baseline questionnaire collects data on demographics and household characteristics, health and COVID-19 related symptoms, test results, potential exposures, and compliance with pandemic measures. At the visit, the informed consent was signed and completeness of the questionnaire was checked and completed if necessary. A 10 mL blood sample was then taken for the seroprevalence testing. Participants that did not show up to their scheduled enrollment visit were contacted again to schedule a new appointment. Further data on demographic, clinical, and sexual characteristics were collected within the frame of the SwissPrEPared study. These data were collected from all participants digitally via the SwissPrEPared web application, described in detail elsewhere. 1,21 In brief, the web application collects health (e.g. symptoms) and behavioral (e.g. number of sexual partners) data from participants via a digitally administered survey and integrates it with clinical and lab-based data (e.g. test results) in one comprehensive database that streamlines the continuity of medical care for this population. After participants consented to the Corona Immunitas study and filled out the Corona Immunitas baseline questionnaire, longitudinal data on number of sexual partners, sexual behavior change during the pandemic, PrEP use, dating app use, education, other medical diagnoses, and COVID-19 vaccine status were extracted from the SwissPrEPared database. Serological testing Participants were considered to have a positive test result if they tested positive for either IgG or IgA antibodies. As in all Corona Immunitas studies, the Sensitive Anti-SARS-CoV-2 Spike Trimer Immunoglobulin Serological (SenASTrIS) Luminex binding assay was used. 29 It was developed by the Vaud Central University Hospital (CHUV), the Swiss Federal Institute of Technology in Lausanne (EPFL), and the Swiss Vaccine Center, has a specificity of 99.7% and sensitivity of 96.6% at 15 days after infection, and has been validated in the general population as well as specific subgroups. 29 Statistical analysis Descriptive statistics for the overall study population and by seropositivity status were calculated using median and interquartile range (IQR) for continuous variables and counts and percentages for categorical variables. To calculate the mean number of sexual partners during the study period, the number of sexual partners reported in the SwissPrEPared followup questionnaire was averaged over all followup questionnaires filled out between March 1, 2020 and October 6, 2020. For questions from the repeated SwissPrEPared followup survey where participants had multiple appointments during that time frame and may have answered differently, we took the most recent answer (e.g. changes in sexual behavior during the pandemic). Confidence intervals (CI) for binomial proportions were produced using the Clopper-Pearson confidence intervals (CI) in base R (binom.test). To calculate the overall prevalence of antibodies in both the study population and the population comparison group, we adjusted for sensitivity and specificity using a Bayesian framework. The posterior distributions for the true prevalence rates were derived by applying Bayes' theorem, assuming beta-distributed priors for the parameters, and incorporating the known test sensitivity/specificity of the antibody test. The adjusted prevalence and associated 95% credible intervals were reported. To determine whether there was a higher presence of COVID-19 antibodies in the SwissPrEPared population versus the general Corona Immunitas population-based sample from the same time period, propensity score matching was performed to balance key demographic characteristics (age, household size, trips abroad, education). Because the SwissPrEPared population was predominantly male (99%), analyses with the Corona Immunitas population were restricted to men and those 65 years or below. The aim of this analysis was to estimate the average marginal effect of being a member of the cohort taking PrEP during the pandemic while accounting for confounding by the included covariates. The propensity score was estimated using full matching on the propensity score and a probit regression of cohort membership on the covariates, which yielded better balance than did a logistic regression. The relative risk (RR) of being positive for COVID-19 antibodies in the SwissPrEPared population versus the general Corona Immunitas population was estimated along with its associated 95% CI. Matching was performed using the MatchIt package, 30 and covariate balance was assessed using cobalt, 31 both in R Version 4.2.3. 32 To determine which predictors were associated with presence of COVID-19 antibodies in both the SwissPrEPared and general Corona Immunitas population of the same time period, exploratory logistic regression was performed and odds ratios (OR) and their associated 95% CI were reported. Results Study Population A total of 218 participants were enrolled in the Corona Immunitas study from the SwissPrEPared cohort. This represents 31% (218/693) of the participants in the SwissPrEPared study that visited Checkpoint Zurich during the study time period. Participants were all assigned male at birth, and almost all had a male gender identity (99%, 1% female, 1% other), Swiss (73%), German speaking (71%), highly educated (73% completed a higher technical or university degree), and employed or self-employed (85%). The median age was 40.0 (IQR: 34.0, 45.8). Most lived alone (45%) or in a household with one other person (42%). Demographic characteristics were very similar between those who were seropositive and seronegative for SARS-CoV-2 (Table 1, Figure 1). Of the 218 participants enrolled in the study, 19 tested positive for SARS-CoV-2 antibodies, corresponding to an adjusted prevalence of 8.7% (95% credible interval: 5.7-13.2%). Table 1. Demographic and health characteristics of study participants [n (%) or median (IQR)]. Total COVID-19 status Positive Negative Participants 218 19 (9%) 199 (91%) Male gender identity 216 (99%) 19 (100%) 197 (99%) Age 40.0 (34.0, 45.8) 38.0 (35.0, 45.0) 40.0 (33.5, 46.0) Swiss nationality 160 (73%) 15 (79%) 145 (73%) Never smoker 124 (57%) 13 (68%) 111 (56%) Additional household members 1.0 (0, 1.0) 0 (0, 1.0) 1.0 (0, 1.0) Number of trips abroad February-October 2020 2.0 (0.8,3.0) 2.0 (1.0, 3.5) 2.0 (0, 3.0) Ever vaccinated against flu 89 (48%) 6 (38%) 83 (49%) EuroQoL self-rated health 88.5 82.5 89.0 Obligatory schooling 1 (0.5%) 0 (0%) 1 (1%) Vocational 34 (16%) 3 (16%) 31 (16%) Matura 23 (11%) 3 (16%) 20 (10%) Higher technical degree 61 (28%) 5 (26%) 56 (28%) University 98 (45%) 8 (42%) 90 (45%) Missing 1 0 1 Employment Employed 167 (77%) 15 (79%) 152 (76%) Self-employed 18 (8%) 1 (5%) 17 (9%) Studying 15 (7%) 1 (5%) 14 (7%) Unemployed 13 (6%) 1 (5%) 12 (6%) Figure 1. Overall comparison of differences in characteristics, social contacts, compliance with social distancing, and sexual risk behavior between those seropositive and seronegative. Differences between the seropositive and seronegative are ordered from greatest to least except for within the sexual risk taking behavior panel. Health risk behaviors and COVID-19 seropositivity Those who were seropositive were less likely to have ever been vaccinated against flu (38% vs. 49%). Compliance with recommended social distancing and hygiene measures was similar across those seropositive and seronegative, although the seropositive were slightly less likely to comply with stay-at-home orders (Table 2, Figure 1). Both groups reduced their social outings during the first lockdown period, but the seronegative were more socially active before, during, and after the first lockdown period, despite the fact that the seropositive were more likely to live alone (Table 1, Figure 1). Participants also reported during the course of the regular SwissPrEPared study whether they later received a COVID-19 vaccination; vaccine uptake was very high, with 94% of both the seropositive and seronegative receiving a COVID-19 vaccination (Table 2, Figure 1, n=172 (79%) of participants reported COVID-19 vaccination status). Table 2. Differences in compliance with social distancing measures of study participants seropositive and seronegative before, during, and after the first lockdown in March 2020 [n (%) or median (IQR)]. A score of 5 corresponds to the highest compliance levels (“always”). Total COVID-19 status Positive Negative Participants 218 19 (9%) 199 (91%) How often** have you in the last 7 days… Followed social distancing*** measures? 4.0 (4.0, 4.0) 4.0 (4.0, 4.0) 4.0 (4.0, 4.0) Stayed home when possible? 3.0 (2.0, 4.0) 3.0 (1.5, 4.0) 3.0 (2.0, 4.0) Worn a mask? 4.0 (4.0, 5.0) 4.0 (4.0, 5.0) 4.0 (4.0, 5.0) Increased hygiene measures**** 4.0 (4.0, 5.0) 4.0 (4.0, 5.0) 4.0 (4.0, 5.0) Average number of contacts with persons outside the household per week (>15 minutes) Pre-lockdown (until mid-March 2020) 15.0 (7.0, 25.0) 10.0 (5.0, 20.0) 15.0 (7.2, 30.0) Lockdown (mid-March to mid-May) 2.0 (1.0, 5.0) 2.0 (0.5, 4.0) 2.0 (1.0, 5.0) Present day (time point of survey) 7.5 (4.0, 15.0) 5.0 (3.5, 10.0) 8.0 (4.0, 15.0) *172 participants (79%) reported whether they later got a COVID-19 vaccination **Participants answered on a scale from 1 to 5, corresponding to the following frequencies: 1: never, 2: rarely, 3: sometimes, 4: often, 5: always. ***No handshakes or hugs, maintain 2m distance from other people ****Regular handwashing, sneezing into the elbow, using tissue Sexual behaviors and COVID-19 seropositivity 185 (85%) of participants filled in at least one follow-up questionnaire about sexual behaviors between March 1, 2020 and October 6, 2020. The differences are summarized in Table 3 and Figure 1. The median number of partners reported was lower among those who were seropositive (3.8, 5.0). Of note, 33% (n=5) of those seropositive who answered the survey did not report having sexual contacts at all during the study period. The use of dating apps was also slightly lower among those who were seropositive (75% vs. 89%), although the majority of both groups used online dating apps. Those who were seropositive were also more likely to have reduced their dating app use during the pandemic (56% vs. 34%). A similar number of people were diagnosed with an STI during the study period in the seropositive and seronegative groups (82% vs. 77%). In a logistic model including only mean partner count and number of trips abroad during the pandemic in the SwissPrEPared study population only (n=185), increasing mean partner count was not associated with seropositivity (OR: 0.9, 95% CI: 0.8, 1.0), but increasing number of trips abroad was marginally associated (p=0.06, OR: 1.14, 95% CI: 1.0, 1.3). Table 3. Differences in sexual behaviors of study participants seropositive and seronegative before, during, and after the first lockdown in March 2020 [n (%) or median (IQR)]. Follow-up questionnaires were included if they were filled out between March 1, 2020 and October 6, 2020. Total COVID-19 status Positive Negative Participants who completed at least one survey 185 (85%) 16 (84%) 169 (85%) Number of surveys 330 30 300 Currently taking PrEP 164 (89%) 14 (88%) 150 (89%) Partner count* 5.0 (2.5, 9.0) 3.8 (2.5, 5.1) 5.0 (2.5, 9.5) Changes in sexual behavior during the pandemic I only had sex with my steady partner 12 (7%) 0 12 (8%) I made an agreement with one of my sexual partners to only have sex with each other (“quarantine buddy”) 3 (2%) 0 3 (2%) I didn’t have sexual contacts during that time 21 (13%) 5 (33%) 16 (11%) I reduced my sexual contacts 110 (67%) 9 (60%) 101 (67%) I didn’t change my sexual behavior 19 (12%) 1 (7%) 18 (12%) I had more sexual contacts 0 0 0 Missing 20 1 19 Use dating apps 117 (88%) 9 (75%) 108 (89%) Use dating apps: missing 52 4 48 Changes in dating app behaviors during the pandemic among those using dating apps (n=117) Use the same 24 (22%) 1 (11%) 23 (23%) Fewer online dates 38 (36%) 5 (56%) 33 (34%) Use more for chatting than sex 41 (38%) 3 (33%) 38 (39%) More online dates 3 (3%) 0 3 (3%) Other 1 (1%) 0 1 (1%) *If participants filled out more than one follow-up survey, the number of partners they reported was averaged across all their follow-up surveys Comparison with general population in Zurich Of the 218 participants enrolled in the Corona Immunitas study, 19 tested positive for SARS-CoV-2 antibodies,corresponding to an adjusted prevalence of 8.7% (95% credible interval: 5.7-13.2%). When restricted to those with primary residence in Zurich (n=195, 89%), the prevalence remained 8.7% (95% CI: 5.5-13.5%), which was slightly elevated compared to that of the general population of male 20-65 year old in Zurich during that time period (5.5%, 95% credible interval: 3.8–8.2%). The estimated RR for the SwissPrEPared cohort compared to the general Corona Immunitas population after propensity score matching (Figure 2) was 1.46 (95% CI: 0.53, 4.0), indicating a 46% increased risk of SARS-CoV-2 positivity for the SwissPrEPared cohort, although not statistically significant. Figure 2. Comparison of the differences in distribution of age, number of people living in the same household, number of trips abroad February to October 2020, and education among SwissPrEPared participants (black line) and the Corona Immunitas general male population aged 20-65 in Zurich (grey line) using density plots. The left panel shows the differences before matching and the right panel shows the differences after matching. To see which of these factors were most strongly associated with COVID-19 infections in the pooled sample of SwissPrEPared and Corona Immunitas participants, we conducted a separate logistic regression model (Table 2). The odds of COVID-19 infection increased by 1% for every additional year of age, 5% for every additional household member, 9% for every additional trip abroad, 97% for being a member of SwissPrEPared, and 450% for those who completed only obligatory schooling (vs. having completed a university degree or higher), after adjusting for the covariates in Table 2. Only the number of trips abroad was statistically significantly associated with risk of COVID-19 seropositivity. Table 2. Predictors of COVID-19 infection in a pooled logistic regression analysis of SwissPrEPared and general male population participants. As there was no data on sexual behavior from the general male population, these variables were omitted from the model. OR 95% CI Age 1.01 0.99, 1.04 Number of additional household members 1.05 0.75, 1.43 Number of trips abroad February-October 2020 1.09 1.02, 1.17 SwissPrEPared 1.97 0.84, 4.79 Education* Obligatory schooling 4.50 0.91, 17.39 Vocational 1.15 0.48, 2.68 Matura 1.23 0.33, 3.66 Higher technical degree 0.93 0.38, 2.15 The odds ratios in bold are those significantly associated with the odds of having a health event that day (95% confidence interval does not cross the null value of 1). *Comparison group: those who completed a university degree or higher. Discussion Our study provides evidence that the risk of COVID-19 seropositivity among those taking PrEP was higher than in the general population in Zurich in the first wave of the COVID-19 pandemic in Switzerland. This risk did not appear to be associated with the number of sexual partners that SwissPrEPared participants reported during the first lockdown, however; in fact, 33% of seropositive participants did not report having any sexual contacts at all. This, linked with the finding that social contacts during the first wave of the pandemic were counterintuitively lower among those who were seropositive, suggests that sexual behaviors were not strongly linked with COVID-19 seropositivity during this time period. Those who were seropositive were more likely to be living alone and less likely to have ever received a flu vaccination, but the risk factor investigated in this study that was most robustly linked with SARS-CoV-2 seropositivity in both the general population and the SwissPrEPared population was the number of trips abroad during the pandemic. While sexual behavior did not appear to be linked with increased risk of SARS-CoV-2 seropositivity within the SwissPrEPared population during the first pandemic wave, there was still a 46% increased risk of infection with SARS-CoV-2 compared with the general male Corona Immunitas population in Zurich after propensity score matching for age, travel, household size, and education. The population of SwissPrEPared participants differs in important ways with that of the general male population from Corona Immunitas (younger, more highly educated, more often living alone, travel more frequently). It may be that other, unmeasured factors account for this increased risk. It is well known that cluster infections (e.g. within family or friend groups) played an important role in the early transmission of COVID-19, 33 meaning that the risk is not particularly linked to individual characteristics, but instead social group membership. Differences in SARS-COV-2 seropositivity between the cohort taking PrEP and the general population The study shows that the prevalence of SARS-CoV-2 infection among participants taking PrEP in Zurich was higher than that of the general Zurich male population from the Corona Immunitas study (prevalence 8.7% vs 5.5%) during the first pandemic wave. This increased risk persists even after propensity score matching the two populations on some key characteristics, such as age, education, household size, and international travel, although the difference in absolute terms is not large. As is true in other cohorts of people taking PrEP, 34 there are key demographic differences between this group and the general population. Although we were able to match the two populations based on these five key characteristics, we were not able to match on other key demographic characteristics that may also have been related to risk of COVID-19 transmission (e.g. profession and occupational exposures, pre-existing health conditions). 35 – 37 Health and sexual behaviors and COVID-19 transmission in the cohort taking PrEP Participants taking PrEP who were seropositive for SARS-CoV-2 differed in some key health behaviors and attitudes. Lifetime flu vaccine uptake was higher in the seronegative group (49% vs 38%), which may translate to their risk attitude and other health behaviors regarding infectious disease in general, known as the healthy vaccine effect. 38 Other studies have also found that those who were previously vaccinated against the flu had decreased risk of COVID-19 infection. 39 These participants may also have been more likely to take protective measures against other infectious diseases, resulting in lower levels of exposure to COVID-19. Seropositive participants were more likely to be living alone. While it is well established that the pandemic had adverse effects on the mental health of those living alone, 40 there is less evidence on how living alone affected COVID-19 transmission and choices around protective behavior. However, a meta-analysis on household transmission found that counterintuitively those living in households with three or more contacts had higher secondary attack rates than those living in households with only one contact. 41 More studies are needed. The behavioral finding most robustly associated with increased risk of COVID-19 seropositivity is travel abroad. The important role of travel abroad in infection and transmission of COVID-19 in the early stages of the pandemic has been established in other studies. 42 , 43 SwissPrEPared participants showed high compliance with social distancing measures. This high level of compliance was similar among both the seropositive and the seronegative. The overwhelming majority of study participants (94%) also later received the COVID-19 vaccination. The results of this study also indicate that SwissPrEPared participants reduced their sexual contacts during the pandemic, similar to what was reported in the United States, Israel, Brazil, and Australia 5 – 8 . This contrasts with what was found in a 2021 German study of PrEP users, which found no change in sexual behavior compared to pre-pandemic, but a similar rate of seroconversion as that of the general population. 17 Other studies from the United States that recruited through dating applications suggested that MSM did not change their sexual behavior or even increased the number of sexual partners during the pandemic, but that may reflect that these populations were recruited from those actively on dating applications during the pandemic. 9 , 10 Another study from the US found age related differences in sexual behavior during the pandemic, with younger MSM having large decreases in testing and PrEP use, but only small reductions in numbers of sexual partners. 44 It is surprising that reported levels of social contacts were lower among the seropositive compared with the before, during, and after the pandemic. It may have been that these participants were able to safely create opportunities to socialize and/or engage in sexual activities while only minimally increasing transmission risk (e.g. through creating “pods”). It is also possible that these data reflect a reporting bias; i.e., that participants that were aware that they had had COVID-19 underreported their social contacts during the pandemic. However, seropositive participants also reported fewer numbers of sexual partners during the study period (median 3.8 vs. 5.0). Since these numbers were reported in real time during the pandemic and most likely prior to knowledge of COVID-19 status, it is unlikely that they were affected by reporting bias. Finally, it may be that those who were symptomatic may have been more likely to isolate after their symptomatic episode, or during specific time periods during the pandemic. Future studies on these behavioral aspects of sexual health could incorporate qualitative research to better understand these findings. The lack of association of education and other sociodemographic characteristics with seropositivity is similar to what was found in the overall Swiss population in the first wave of the pandemic, where only younger age was associated with increased seropositivity. 24 This may reflect high compliance with overall social distancing measures during the initial phases of the pandemic in Switzerland. Limitations This study is subject to some limitations. Participants in this study were those that did not discontinue use of PrEP during the initial pandemic lockdown, meaning that they are likely less risk averse than participants that did stop attending their PrEP visits during this time. The number of people who were seropositive in this cohort was small (n = 19), meaning that the data on behavioral and demographic patterns in seropositivity need to be interpreted with caution. In addition, similar information on sexual behaviors during the lockdown was not available for sexually active individuals not on PrEP during this time period, so it is not possible to compare this group with other sexually active groups (e.g. heterosexuals). As mentioned above, there is a possibility of reporting bias, with those who had symptoms of COVID-19 remembering being more cautious than they really were. However, data on sexual behavior was reported as part of routine PrEP follow-up visits, making it unlikely that underreporting is linked to COVID-19 status. Finally, there was likely residual confounding in the comparison between the cohort of people taking PrEP and the general male population in Zurich. Conclusions Overall, COVID-19 seropositivity during the first pandemic wave was slightly elevated in a cohort of people taking PrEP compared to the general male population in Zurich, Switzerland. Our study suggests that at least in the first wave of lockdown, socializing and sexual activity were less important than other factors in COVID-19 seropositivity among those taking PrEP. While we cannot retrospectively identify precisely what those factors were, the association of seropositivity with international travel and deprioritization of health protection measures such as vaccination suggest that these factors may have played a role. Those who were less likely to prioritize precautionary measures such as vaccines may also have been less likely to prioritize complying with social distancing measures. Declarations Funding This study is part of Corona Immunitas research network, coordinated by the Swiss School of Public Health (SSPH+), and funded by fundraising of SSPH+ including funds of the Swiss Federal Office of Public Health and private funders (ethical guidelines for funding stated by SSPH+ were respected). Financial support from the Swiss Federal Office of Public Health (FOPH) was received by the SwissPrEPared program and study. The funding bodies had no influence on the design, conduct, analysis or interpretation of the study, nor on the decision to publish, the preparation or revisions of the manuscript. Competing Interests The authors have no relevant financial or non-financial interests to disclose. Ethics Approval This study was performed in line with the principles of the Declaration of Helsinki. The SwissPrEPared study (NCT03893188) was approved by the lead ethical committee (EC) in Zurich on 14 May 2019 (BASEC Nr. 2018-02015), followed by the approval of all ECs from the other cantons. The Corona Immunitas study was approved by the lead EC in Zurich (BASEC Nr. 2020-01247), followed by the approval of all ECs from the other cantons. Consent Informed consent was obtained from all individual participants included in the study. Availability of data and materials De-identified individual participant data underlying the findings and the codes used for this study will be available for researchers. Requests can be made to the Executive Committee of Corona Immunitas [https://zenodo.org/record/7520125] or to the corresponding author. Author Contributions Conceptualization: Benjamin Hampel, Anja Frei, Andrea Farnham; Methodology: Benjamin Hampel, Anja Frei, Matthias Reinacher, Milo A. Puhan, Jan S. Fehr, ; Formal analysis and investigation: Andrea Farnham; Writing - original draft preparation: Andrea Farnham; Writing - review and editing: Benjamin Hampel, Julia Kopp, Larissa J. Schori, Olivia J. Kotoun, Matthias Reinacher, Manuela Rasi, Milo A. Puhan, Jan S. Fehr; Funding acquisition: Benjamin Hampel, Milo A. Puhan, Jan S. Fehr; Supervision: Benjamin Hampel, Anja Frei, Jan S. Fehr, Milo A. Puhan Acknowledgements We would like to thank the participants in the study for their time and and contributions to the study, as well as the study administrative staff for their dedicated support of the study. References Winter BL, Hovaguimian F, Kouyos RD, et al. Changes in mental and sexual health among MSM using HIV pre-exposure prophylaxis during the SARS-CoV-2 pandemic: longitudinal analysis of the SwissPrEPared cohort study. Swiss Med Wkly 2022; 152 : w30192. Bzdok D, Dunbar RIM. Social isolation and the brain in the pandemic era. Nat Hum Behav 2022; 6 : 1333–43. 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DOI:https://doi.org/10.2807/1560-7917.ES.2022.27.31.2200561. Frei A, Kaufmann M, Amati R, et al. Development of hybrid immunity during a period of high incidence of Omicron infections. Int J Epidemiol 2023; 52 : 1696–707. Tancredi S, Chiolero A, Wagner C, et al. Seroprevalence trends of anti-SARS-CoV-2 antibodies and associated risk factors: a population-based study. Infection 2023; 51 : 1453–65. Amati R, Piumatti G, Franscella G, et al. Trajectories of Seroprevalence and Neutralizing Activity of Antibodies against SARS-CoV-2 in Southern Switzerland between July 2020 and July 2021: An Ongoing, Prospective Population-Based Cohort Study. Int J Environ Res Public Health 2023; 20 . DOI:10.3390/ijerph20043703. West EA, Kotoun OJ, Schori LJ, et al. Seroprevalence of SARS-CoV-2 antibodies, associated factors, experiences and attitudes of nursing home and home healthcare employees in Switzerland. BMC Infect Dis 2022; 22 : 259. West EA, Anker D, Amati R, et al. Corona Immunitas: study protocol of a nationwide program of SARS-CoV-2 seroprevalence and seroepidemiologic studies in Switzerland. Int J Public Health 2020; 65 : 1529–48. Bruggmann P, Senn O, Frei A, Puhan MA, Fehr J, Falcato L. High SARS-CoV-2 seroprevalence but no severe course of COVID-19 disease among people on opioid agonist treatment in Zurich: a cross-sectional study. Swiss Med Wkly 2022; 152 : w30122. Fenwick Craig, Croxatto Antony, Coste Alix T., et al. Changes in SARS-CoV-2 Spike versus Nucleoprotein Antibody Responses Impact the Estimates of Infections in Population-Based Seroprevalence Studies. J Virol 2021; 95 : 10.1128/jvi.01828-20. Ho D, Imai K, King G, Stuart EA. MatchIt: Nonparametric Preprocessing for Parametric Causal Inference. J Stat Softw 2011; 42 : 1–28. Greifer N. cobalt: Covariate Balance Tables and Plots. 2023 https://ngreifer.github.io/cobalt/. R Core Team. R: A Language and Environment for Statistical Computing. Vienna, Austria: R Foundation for Statistical Computing, 2023 https://www.R-project.org/. Liu T, Gong D, Xiao J, et al. Cluster infections play important roles in the rapid evolution of COVID-19 transmission: A systematic review. Int J Infect Dis 2020; 99 : 374–80. Westmoreland DA, Pantalone DW, Patel VV, Hoover D, Nash D, Grov C. Demographic, Behavioral, and Geographic Differences Between Men, Transmen, and Transwomen Currently on PrEP, Former PrEP Users, and Those Having Never Used PrEP. AIDS Behav 2020; 24 : 1304–11. Charlett A, Hiironen I, Hughes GJ, et al. Workplace exposures associated with COVID-19: evidence from a case-control study with multiple sampling periods in England, August–October 2020. Epidemiol Infect 2022; 150 : e99. Nguyen LH, Drew DA, Graham MS, et al. Risk of COVID-19 among front-line health-care workers and the general community: a prospective cohort study. Lancet Public Health 2020; 5 : e475–83. Murti M, Achonu C, Smith BT, et al. COVID-19 Workplace Outbreaks by Industry Sector and Their Associated Household Transmission, Ontario, Canada, January to June, 2020. J Occup Environ Med 2021; 63 . https://journals.lww.com/joem/fulltext/2021/07000/covid_19_workplace_outbreaks_by_industry_sector.5.aspx. Fine PEM, Chen RT. Confounding in Studies of Adverse Reactions to Vaccines. Am J Epidemiol 1992; 136 : 121–35. Huang K, Lin S-W, Sheng W-H, Wang C-C. Influenza vaccination and the risk of COVID-19 infection and severe illness in older adults in the United States. Sci Rep 2021; 11 : 11025. Eoin McElroy, Emily Herrett, Kishan Patel, et al. Living alone and mental health: parallel analyses in UK longitudinal population surveys and electronic health records prior to and during the COVID-19 pandemic. BMJ Ment Health 2023; 26 : e300842. Madewell ZJ, Yang Y, Longini IM Jr, Halloran ME, Dean NE. Household Transmission of SARS-CoV-2: A Systematic Review and Meta-analysis. JAMA Netw Open 2020; 3 : e2031756–e2031756. Böhm S, Böhmer MM, Chen D, et al. Epidemiology and transmission characteristics of early COVID-19 cases, 20 January–19 March 2020, in Bavaria, Germany. Epidemiol Infect 2021; 149 : e65. Menkir TF, Chin T, Hay JA, et al. Estimating internationally imported cases during the early COVID-19 pandemic. Nat Commun 2021; 12 : 311. Goodreau SM, Delaney KP, Zhu W, et al. Impacts of COVID-19 on sexual behaviors, HIV prevention and care among men who have sex with men: A comparison of New York City and Metropolitan Atlanta. PLOS ONE 2023; 18 : e0282503. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 02 Nov, 2024 Read the published version in BMC Public Health → Version 1 posted Editorial decision: Revision requested 12 Sep, 2024 Reviews received at journal 26 Jul, 2024 Reviewers agreed at journal 22 Jul, 2024 Reviews received at journal 21 Jun, 2024 Reviewers agreed at journal 29 May, 2024 Reviewers invited by journal 27 May, 2024 Editor invited by journal 01 Apr, 2024 Editor assigned by journal 29 Mar, 2024 Submission checks completed at journal 29 Mar, 2024 First submitted to journal 26 Mar, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4169289","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":286039577,"identity":"10a53b21-2867-41cf-a5f6-dd3a47a6c493","order_by":0,"name":"Andrea Farnham","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA40lEQVRIiWNgGAWjYHACAxDBD8RsQGzDwCDBwMBMjBbJBoiWNNK1HCashX9287YPH2oYJPhnnz324GfO+cT5sxsYPxfg0SJx51jxzBnHGCQkzuWlG/Zuu53YOOcAs/QMfNbcyDFm5mFjqGM4w2MmwQvU0iyRwMbMg0eHPEjLn38MEvJALZJ/t51LbCOkxQCkhbGNQcIAqEWad9uBxB5CWgxvpBUz9vZJSBiCtMhuSzaeIZHYLI1Pi9yN5M0MP77ZSMiBHPZ2m53s/BnJBz/j0wIFEsgcxgbCGkbBKBgFo2AU4AUA1dVE7yd3DWsAAAAASUVORK5CYII=","orcid":"","institution":"University of Zurich","correspondingAuthor":true,"prefix":"","firstName":"Andrea","middleName":"","lastName":"Farnham","suffix":""},{"id":286039578,"identity":"85d2f8e7-edcb-4e6f-927f-fafc939b43ae","order_by":1,"name":"Anja Frei","email":"","orcid":"","institution":"University of Zurich","correspondingAuthor":false,"prefix":"","firstName":"Anja","middleName":"","lastName":"Frei","suffix":""},{"id":286039579,"identity":"ed5d1419-d38e-454b-b334-395fa3806d5e","order_by":2,"name":"Julia Kopp","email":"","orcid":"","institution":"University of Zurich","correspondingAuthor":false,"prefix":"","firstName":"Julia","middleName":"","lastName":"Kopp","suffix":""},{"id":286039580,"identity":"0f47df5e-a8d0-49e1-a4d7-4e4f57dba8ec","order_by":3,"name":"Larissa J. 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Fehr","email":"","orcid":"","institution":"University of Zurich","correspondingAuthor":false,"prefix":"","firstName":"Jan","middleName":"S.","lastName":"Fehr","suffix":""},{"id":286039586,"identity":"9e7b4e5e-8501-434a-974b-9e4dd40af1df","order_by":9,"name":"Benjamin Hampel","email":"","orcid":"","institution":"University of Zurich","correspondingAuthor":false,"prefix":"","firstName":"Benjamin","middleName":"","lastName":"Hampel","suffix":""}],"badges":[],"createdAt":"2024-03-26 10:58:51","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4169289/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4169289/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12889-024-20514-9","type":"published","date":"2024-11-02T16:20:29+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":54039255,"identity":"6ed8485c-1d11-4788-b7ad-5d9894a03bf4","added_by":"auto","created_at":"2024-04-03 17:21:06","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":136280,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOverall comparison of differences in characteristics, social contacts, compliance with social distancing, and sexual risk behavior between those seropositive and seronegative. Differences between the seropositive and seronegative are ordered from greatest to least except for within the sexual risk taking behavior panel.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4169289/v1/fb4954d50fe72d9e9287e018.png"},{"id":54039256,"identity":"d9cd7127-3fb2-4b45-a9d1-92b1d71be25c","added_by":"auto","created_at":"2024-04-03 17:21:06","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":47630,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eComparison of the differences in distribution of age, number of people living in the same household, number of trips abroad February to October 2020, and education among SwissPrEPared participants (black line) and the Corona Immunitas general male population aged 20-65 in Zurich (grey line) using density plots. The left panel shows the differences before matching and the right panel shows the differences after matching.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4169289/v1/dd440eb7ce88506a4e6c0410.png"},{"id":68207254,"identity":"c1058508-106d-4c3f-8974-0f72ec990d15","added_by":"auto","created_at":"2024-11-04 16:36:12","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1782878,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4169289/v1/ea7a2cd0-18ab-442c-8a4f-8d348373b84a.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Sexual behaviours among MSM during the first COVID-19 lockdown not associated with risk of COVID-19 infection","fulltext":[{"header":"Background","content":"\u003cp\u003eSoon after the emergence of SARS-CoV-2, unprecedented restrictions on social contact and mobility were implemented globally to contain the virus, including rules on restricting sexual contacts. These restrictions often had unintended consequences, especially on mental health,\u003csup\u003e1\u003c/sup\u003e stress, substance use, and sleep patterns.\u003csup\u003e2–4\u003c/sup\u003e These consequences were not evenly distributed among the population, with the burden of the mental health effects of social distancing falling disproportionately on vulnerable populations such as adolescents, young people, and people with minority sexual orientation or gender identity.\u003csup\u003e4–6\u003c/sup\u003e In Switzerland, social distancing measures were implemented starting in March 2020, and the strongest restrictions occurred over the first waves of the pandemic.\u003c/p\u003e\n\u003cp\u003eSocial distancing measures were particularly difficult for people with non-steady sexual partners to implement.\u003csup\u003e6\u003c/sup\u003e Sexual behavior is complex and cannot be changed easily; previous research has shown that mate-seeking motives (especially among young men) was one of the strongest predictors of lack of compliance with social distancing measures.\u003csup\u003e7\u003c/sup\u003e People who are not in steady sexual relationships are more likely to live alone and thus more likely to suffer from social and mental isolation due to the restrictions. A study in Germany showed that loneliness, anxiety and depression during the pandemic were particularly high among people with minority sexual orientation or gender identity, and especially those living alone.\u003csup\u003e5\u003c/sup\u003e Some estimates suggest that over 50% of urban households are solitary in many metropolitan areas,\u003csup\u003e2\u003c/sup\u003e and that men having sex with men (MSM) are particularly likely to live alone.\u003csup\u003e6\u003c/sup\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eA robust scientific evidence base has emerged that the first phases of the COVID-19 pandemic had significant effects on sexual behavior worldwide.\u003csup\u003e6,8\u003c/sup\u003e However, few studies focused specifically on people with non-steady sexual partners or the result of changes in their sexual behavior on risk of acquiring SARS-CoV-2.\u003csup\u003e8\u003c/sup\u003e Much of the research in this area has focused on MSM, partly due to pre-existing research on sex behaviors in this population. Most studies on changes in sexual activity among MSM showed reductions in numbers of sexual partners during the first phases of the pandemic.\u003csup\u003e1,9–12\u003c/sup\u003e However, a few studies showed no change or even increases in the number of sexual partners in this population during the first year of the pandemic.\u003csup\u003e13–15\u003c/sup\u003e It still remains poorly understood how social distancing measures during the pandemic affected the sexual health of people not in a steady relationship. It also remains unclear whether sexual contact with non-steady partners was a contributor to the spread of SARS-CoV-2.\u003c/p\u003e\n\u003cp\u003eAs HIV PrEP-exposure prophylaxis (PrEP) is almost exclusively taken by people with multiple sexual partners, some studies have taken advantage of existing PrEP cohorts to investigate how the pandemic investigated sexual risk taking.\u003csup\u003e1,16–20\u003c/sup\u003e However, these studies suffered from lack of a comparable population cohort to understand whether risk was elevated in PrEP cohorts compared to other populations with similar demographic characteristics. In our study, we were able to integrate people taking PrEP into an existing population level seroprevalence study (Corona Immunitas) to better examine and compare the influence of sexual behavior on the COVID-19 pandemic on this population.\u003c/p\u003e\n\u003cp\u003eThe aim of this study was to (i) assess whether the SARS-CoV-2 seropositivity after the first pandemic wave among people using PrEP in Zurich differed from that of a demographic matched population level comparison group, (ii) describe risk factors for SARS-CoV-2 seropositivity in this population, and (iii) determine whether sexual contact with non-steady partners was associated with SARS-CoV-2 seropositivity.\u0026nbsp;\u003c/p\u003e"},{"header":"Methods","content":"\u003ch2\u003eStudy design, setting and participants\u003c/h2\u003e\n\u003cp\u003eThis study is a cross-sectional study nested within two ongoing studies: SwissPrEPared and Corona Immunitas. The study was conducted between July 2020 and October 2020, a period corresponding to the end of the first pandemic wave and the beginning of the second.\u003c/p\u003e\n\u003ch3\u003eSwissPrEPared national program and cohort study\u003c/h3\u003e\n\u003cp\u003eThe SwissPrEPared program is a large, ongoing nation-wide Swiss cohort of PrEP users. Individuals are eligible to participate if they are ≥18 years old and express interest in PrEP in one of the participating medical centers. The enrollment for the SwissPrEPared study is detailed elsewhere,\u003csup\u003e21\u003c/sup\u003e but in brief, all persons interested in PrEP and 18 years of age or older living in Switzerland are eligible for the SwissPrEPared study. Following international recommendations, three monthly screenings for counseling and STI screening are recommended for those on daily PrEP and at least six monthly screenings for those on event-based PrEP. Active participants of the SwissPrEPared study who attended Checkpoint Zurich for their routine PrEP appointments between July 15 and October 6, 2020 (before the second wave of the COVID-19 pandemic hit Switzerland), were eligible for participation in the Corona Immunitas substudy. \u0026nbsp; Checkpoint Zurich is the largest PrEP center in Switzerland.\u0026nbsp;\u003c/p\u003e\n\u003ch3\u003eCorona Immunitas national research program\u003c/h3\u003e\n\u003cp\u003eCorona Immunitas is a nation-wide Swiss research program of cross-sectional and longitudinal SARS-CoV-2 seroprevalence studies that investigated the spread and impact of infection with SARS-Cov-2 in Switzerland over six phases (https://www.corona-immunitas.ch/en/).\u003csup\u003e22–26\u003c/sup\u003e To ensure comparability, a standardized protocol (ISRCTN18181860)\u0026nbsp;\u003csup\u003e27\u003c/sup\u003e including the same baseline questionnaire and serological testing was administered in the Swiss general population and in several subpopulations.\u003csup\u003e28\u003c/sup\u003e\u0026nbsp; For this study, we used data from Corona Immunitas phase 2 of the canton of Zurich, for which randomly selected individuals from the general population were recruited using age stratified sampling (20-64 years, ≥65 years) and invited to participate.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe SwissPrEPared study (NCT03893188) was approved by the lead ethical committee (EC) in Zurich on 14 May 2019 (BASEC Nr. 2018-02015), followed by the approval of all ECs from the other cantons. The Corona Imunitas study was approved by the lead EC in Zurich (BASEC Nr. 2020-01247), followed by the approval of all ECs from the other cantons. All participants signed a written informed consent.\u003c/p\u003e\n\u003ch2\u003eProcedures and measurements\u003c/h2\u003e\n\u003cp\u003eA poster with information about the Corona Immunitas study and the study team contact information was placed in the Checkpoint Zurich waiting area. During their routine visits, SwissPrEPared participants were informed about the Corona Immunitas study by their healthcare providers, and given contact information for the study team. Finally, all Checkpoint Zurich SwissPrEPared participants who were not yet enrolled in Corona Immunitas were sent a text message inviting them to enroll. The Corona Immunitas study team contacted all participants by email or telephone, answered questions, arranged an enrollment visit, and sent out an electronic version of the informed consent and Corona Immunitas standardized baseline questionnaire prior to the enrollment visit. The Corona Immunitas standardized baseline questionnaire collects data on demographics and household characteristics, health and COVID-19 related symptoms, test results, potential exposures, and compliance with pandemic measures. At the visit, the informed consent was signed and completeness of the questionnaire was checked and completed if necessary. A 10 mL blood sample was then taken for the seroprevalence testing. Participants that did not show up to their scheduled enrollment visit were contacted again to schedule a new appointment.\u003c/p\u003e\n\u003cp\u003eFurther data on demographic, clinical, and sexual characteristics were collected within the frame of the SwissPrEPared study. These data were collected from all participants digitally via the SwissPrEPared web application, described in detail elsewhere.\u003csup\u003e1,21\u003c/sup\u003e In brief, the web application collects health (e.g. symptoms) and behavioral (e.g. number of sexual partners) data from participants via a digitally administered survey and integrates it with clinical and lab-based data (e.g. test results) in one comprehensive database that streamlines the continuity of medical care for this population. After participants consented to the Corona Immunitas study and filled out the Corona Immunitas baseline questionnaire, longitudinal data on number of sexual partners, sexual behavior change during the pandemic, PrEP use, dating app use, education, other medical diagnoses, and COVID-19 vaccine status were extracted from the SwissPrEPared database.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003eSerological testing\u003c/h2\u003e\n\u003cp\u003eParticipants were considered to have a positive test result if they tested positive for either IgG or IgA antibodies. As in all Corona Immunitas studies, the Sensitive Anti-SARS-CoV-2 Spike Trimer Immunoglobulin Serological (SenASTrIS) Luminex binding assay was used.\u003csup\u003e29\u003c/sup\u003e It was developed by the Vaud Central University Hospital (CHUV), the Swiss Federal Institute of Technology in Lausanne (EPFL), and the Swiss Vaccine Center, has a specificity of 99.7% and sensitivity of 96.6% at 15 days after infection, and has been validated in the general population as well as specific subgroups.\u003csup\u003e29\u003c/sup\u003e\u003c/p\u003e\n\u003ch2\u003eStatistical analysis\u003c/h2\u003e\n\u003cp\u003eDescriptive statistics for the overall study population and by seropositivity status were calculated using median and interquartile range (IQR) for continuous variables and counts and percentages for categorical variables. To calculate the mean number of sexual partners during the study period, the number of sexual partners reported in the SwissPrEPared followup questionnaire was averaged over all followup questionnaires filled out between March 1, 2020 and October 6, 2020. For questions from the repeated SwissPrEPared followup survey where participants had multiple appointments during that time frame and may have answered differently, we took the most recent answer (e.g. changes in sexual behavior during the pandemic). Confidence intervals (CI) for binomial proportions were produced using the Clopper-Pearson confidence intervals (CI) in base R (binom.test). To calculate the overall prevalence of antibodies in both the study population and the population comparison group, we adjusted for sensitivity and specificity using a Bayesian framework. The posterior distributions for the true prevalence rates were derived by applying Bayes' theorem, assuming beta-distributed priors for the parameters, and incorporating the known test sensitivity/specificity of the antibody test. The adjusted prevalence and associated 95% credible intervals were reported.\u003c/p\u003e\n\u003cp\u003eTo determine whether there was a higher presence of COVID-19 antibodies in the SwissPrEPared population versus the general Corona Immunitas population-based sample from the same time period, propensity score matching was performed to balance key demographic characteristics (age, household size, trips abroad, education). Because the SwissPrEPared population was predominantly male (99%), analyses with the Corona Immunitas population were restricted to men and those 65 years or below. The aim of this analysis was to estimate the average marginal effect of being a member of the cohort taking PrEP during the pandemic while accounting for confounding by the included covariates. The propensity score was estimated using full matching on the propensity score and a probit regression of cohort membership on the covariates, which yielded better balance than did a logistic regression. The relative risk (RR) of being positive for COVID-19 antibodies in the SwissPrEPared population versus the general Corona Immunitas population was estimated along with its associated 95% CI. Matching was performed using the MatchIt package,\u003csup\u003e30\u003c/sup\u003e and covariate balance was assessed using cobalt,\u003csup\u003e31\u003c/sup\u003e both in R Version 4.2.3.\u003csup\u003e32\u003c/sup\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTo determine which predictors were associated with presence of COVID-19 antibodies in both the SwissPrEPared and general Corona Immunitas population of the same time period, exploratory logistic regression was performed and odds ratios (OR) and their associated 95% CI were reported.\u0026nbsp;\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003eStudy Population\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA total of 218 participants were enrolled in the Corona Immunitas study from the SwissPrEPared cohort. This represents 31% (218/693) of the participants in the SwissPrEPared study that visited Checkpoint Zurich during the study time period. Participants were all assigned male at birth, and almost all had a male gender identity (99%, 1% female, 1% other), Swiss (73%), German speaking (71%), highly educated (73% completed a higher technical or university degree), and employed or self-employed (85%). The median age was 40.0 (IQR: 34.0, 45.8). Most lived alone (45%) or in a household with one other person (42%). Demographic characteristics were very similar between those who were seropositive and seronegative for SARS-CoV-2 (Table 1, Figure 1). Of the 218 participants enrolled in the study, 19 tested positive for SARS-CoV-2 antibodies, corresponding to an adjusted prevalence of 8.7% (95% credible interval: 5.7-13.2%).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1. Demographic and health characteristics of study participants [n (%) or median (IQR)].\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"44.44444444444444%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eCOVID-19 status\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003ePositive\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003eNegative\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eParticipants\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e218\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e19 (9%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e199 (91%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eMale gender identity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e216 (99%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e19 (100%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e197 (99%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eAge\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e40.0 (34.0, 45.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e38.0 (35.0, 45.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e40.0 (33.5, 46.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eSwiss nationality\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e160 (73%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e15 (79%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e145 (73%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eNever smoker\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e124 (57%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e13 (68%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e111 (56%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eAdditional household members\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e1.0 (0, 1.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e0 (0, 1.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e1.0 (0, 1.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eNumber of trips abroad February-October 2020\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e2.0 (0.8,3.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e2.0 (1.0, 3.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e2.0 (0, 3.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eEver vaccinated against flu\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e89 (48%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e6 (38%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e83 (49%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eEuroQoL self-rated health\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e88.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e82.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e89.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eObligatory schooling\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e1 (0.5%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e0 (0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e1 (1%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eVocational\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e34 (16%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e3 (16%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e31 (16%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eMatura\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e23 (11%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e3 (16%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e20 (10%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eHigher technical degree\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e61 (28%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e5 (26%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e56 (28%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eUniversity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e98 (45%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e8 (42%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e90 (45%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eMissing\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eEmployment\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eEmployed\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e167 (77%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e15 (79%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e152 (76%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eSelf-employed\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e18 (8%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e1 (5%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e17 (9%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eStudying\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e15 (7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e1 (5%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e14 (7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eUnemployed\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e13 (6%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e1 (5%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e12 (6%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eFigure 1. Overall comparison of differences in characteristics, social contacts, compliance with social distancing, and sexual risk behavior between those seropositive and seronegative. Differences between the seropositive and seronegative are ordered from greatest to least except for within the sexual risk taking behavior panel.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eHealth risk behaviors and COVID-19 seropositivity\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThose who were seropositive were less likely to have ever been vaccinated against flu (38% vs. 49%). Compliance with recommended social distancing and hygiene measures was similar across those seropositive and seronegative, although the seropositive were slightly less likely to comply with stay-at-home orders (Table 2, Figure 1). Both groups reduced their social outings during the first lockdown period, but the seronegative were more socially active before, during, and after the first lockdown period, despite the fact that the seropositive were more likely to live alone (Table 1, Figure 1). Participants also reported during the course of the regular SwissPrEPared study whether they later received a COVID-19 vaccination; vaccine uptake was very high, with 94% of both the seropositive and seronegative receiving a COVID-19 vaccination (Table 2, Figure 1, n=172 (79%) of participants reported COVID-19 vaccination status).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eTable 2. Differences in compliance with social distancing measures of study participants seropositive and seronegative before, during, and after the first lockdown in March 2020 [n (%) or median (IQR)]. A score of 5 corresponds to the highest compliance levels (\u0026ldquo;always\u0026rdquo;).\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"44.44444444444444%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eCOVID-19 status\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003ePositive\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003eNegative\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eParticipants\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e218\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e19 (9%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e199 (91%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"100%\" colspan=\"4\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eHow often** have you in the last 7 days\u0026hellip;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eFollowed social distancing*** measures?\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e4.0 (4.0, 4.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e4.0 (4.0, 4.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e4.0 (4.0, 4.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eStayed home when possible?\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e3.0 (2.0, 4.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e3.0 (1.5, 4.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e3.0 (2.0, 4.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eWorn a mask?\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e4.0 (4.0, 5.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e4.0 (4.0, 5.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e4.0 (4.0, 5.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eIncreased hygiene measures****\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e4.0 (4.0, 5.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e4.0 (4.0, 5.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e4.0 (4.0, 5.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"100%\" colspan=\"4\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eAverage number of contacts with persons outside the household per week (\u0026gt;15 minutes)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003ePre-lockdown (until mid-March 2020)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e15.0 (7.0, 25.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e10.0 (5.0, 20.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e15.0 (7.2, 30.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eLockdown (mid-March to mid-May)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e2.0 (1.0, 5.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e2.0 (0.5, 4.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e2.0 (1.0, 5.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003ePresent day (time point of survey)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e7.5 (4.0, 15.0)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e5.0 (3.5, 10.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e8.0 (4.0, 15.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e*172 participants (79%) reported whether they later got a COVID-19 vaccination\u003c/p\u003e\n\u003cp\u003e**Participants answered on a scale from 1 to 5, corresponding to the following frequencies: 1: never, 2: rarely, 3: sometimes, 4: often, 5: always.\u003c/p\u003e\n\u003cp\u003e***No handshakes or hugs, maintain 2m distance from other people\u003c/p\u003e\n\u003cp\u003e****Regular handwashing, sneezing into the elbow, using tissue\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSexual behaviors and COVID-19 seropositivity\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e185 (85%) of participants filled in at least one follow-up questionnaire about sexual behaviors between March 1, 2020 and October 6, 2020. The differences are summarized in Table 3 and Figure 1. The median number of partners reported was lower among those who were seropositive (3.8, 5.0). Of note, 33% (n=5) of those seropositive who answered the survey did not report having sexual contacts at all during the study period. The use of dating apps was also slightly lower among those who were seropositive (75% vs. 89%), although the majority of both groups used online dating apps. Those who were seropositive were also more likely to have reduced their dating app use during the pandemic (56% vs. 34%). A similar number of people were diagnosed with an STI during the study period in the seropositive and seronegative groups (82% vs. 77%).\u003c/p\u003e\n\u003cp\u003eIn a logistic model including only mean partner count and number of trips abroad during the pandemic in the SwissPrEPared study population only (n=185), increasing mean partner count was not associated with seropositivity (OR: 0.9, 95% CI: 0.8, 1.0), but increasing number of trips abroad was marginally associated (p=0.06, OR: 1.14, 95% CI: 1.0, 1.3).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3.\u003c/strong\u003e \u003cstrong\u003eDifferences in sexual behaviors of study participants seropositive and seronegative before, during, and after the first lockdown in March 2020 [n (%) or median (IQR)]. Follow-up questionnaires were included if they were filled out between March 1, 2020 and October 6, 2020.\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"44.44444444444444%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eCOVID-19 status\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003ePositive\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003eNegative\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eParticipants who completed at least one survey\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e185 (85%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e16 (84%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e169 (85%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eNumber of surveys\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e330\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e300\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eCurrently taking PrEP\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e164 (89%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e14 (88%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e150 (89%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003ePartner count*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e5.0 (2.5, 9.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e3.8 (2.5, 5.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e5.0 (2.5, 9.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"100%\" colspan=\"4\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eChanges in sexual behavior during the pandemic\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eI only had sex with my steady partner\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e12 (7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e12 (8%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eI made an agreement with one of my sexual partners to only have sex with each other (\u0026ldquo;quarantine buddy\u0026rdquo;)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e3 (2%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e3 (2%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eI didn\u0026rsquo;t have sexual contacts during that time\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e21 (13%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e5 (33%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e16 (11%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eI reduced my sexual contacts\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e110 (67%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e9 (60%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e101 (67%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eI didn\u0026rsquo;t change my sexual behavior\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e19 (12%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e1 (7%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e18 (12%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eI had more sexual contacts\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eMissing\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e19\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eUse dating apps\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e117 (88%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e9 (75%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e108 (89%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eUse dating apps: missing\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e48\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"100%\" colspan=\"4\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eChanges in dating app behaviors during the pandemic among those using dating apps (n=117)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eUse the same\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e24 (22%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e1 (11%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e23 (23%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eFewer online dates\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e38 (36%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e5 (56%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e33 (34%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eUse more for chatting than sex\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e41 (38%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e3 (33%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e38 (39%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eMore online dates\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e3 (3%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e3 (3%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eOther\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e1 (1%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.22222222222222%\" valign=\"top\"\u003e\n \u003cp\u003e1 (1%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e*If participants filled out more than one follow-up survey, the number of partners they reported was averaged across all their follow-up surveys\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eComparison with general population in Zurich\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOf the 218 participants enrolled in the Corona Immunitas study, 19 tested positive for SARS-CoV-2 antibodies,corresponding to an adjusted prevalence of 8.7% (95% credible interval: 5.7-13.2%). When restricted to those with primary residence in Zurich (n=195, 89%), the prevalence remained 8.7% (95% CI: 5.5-13.5%), which was slightly elevated compared to that of the general population of male 20-65 year old in Zurich during that time period (5.5%, 95% credible interval: 3.8\u0026ndash;8.2%). The estimated RR for the SwissPrEPared cohort compared to the general Corona Immunitas population after propensity score matching (Figure 2) was 1.46 (95% CI: 0.53, 4.0), indicating a 46% increased risk of SARS-CoV-2 positivity for the SwissPrEPared cohort, although not statistically significant.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFigure 2. Comparison of the differences in distribution of age, number of people living in the same household, number of trips abroad February to October 2020, and education among SwissPrEPared participants (black line) and the Corona Immunitas general male population aged 20-65 in Zurich (grey line) using density plots. The left panel shows the differences before matching and the right panel shows the differences after matching.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo see which of these factors were most strongly associated with COVID-19 infections in the pooled sample of SwissPrEPared and Corona Immunitas participants, we conducted a separate logistic regression model (Table 2). The odds of COVID-19 infection increased by 1% for every additional year of age, 5% for every additional household member, 9% for every additional trip abroad, 97% for being a member of SwissPrEPared, and 450% for those who completed only obligatory schooling (vs. having completed a university degree or higher), after adjusting for the covariates in Table 2. Only the number of trips abroad was statistically significantly associated with risk of COVID-19 seropositivity.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2. Predictors of COVID-19 infection in a pooled logistic regression analysis of SwissPrEPared and general male population participants. As there was no data on sexual behavior from the general male population, these variables were omitted from the model.\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"46.11973392461197%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.620842572062084%\" valign=\"top\"\u003e\n \u003cp\u003eOR\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.25942350332594%\" valign=\"top\"\u003e\n \u003cp\u003e95% CI\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"46.11973392461197%\" valign=\"top\"\u003e\n \u003cp\u003eAge\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.620842572062084%\" valign=\"top\"\u003e\n \u003cp\u003e1.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.25942350332594%\" valign=\"top\"\u003e\n \u003cp\u003e0.99, 1.04\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"46.11973392461197%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of additional household members\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.620842572062084%\" valign=\"top\"\u003e\n \u003cp\u003e1.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.25942350332594%\" valign=\"top\"\u003e\n \u003cp\u003e0.75, 1.43\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"46.11973392461197%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eNumber of trips abroad February-October 2020\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.620842572062084%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e1.09\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.25942350332594%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e1.02, 1.17\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"46.11973392461197%\" valign=\"top\"\u003e\n \u003cp\u003eSwissPrEPared\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.620842572062084%\" valign=\"top\"\u003e\n \u003cp\u003e1.97\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.25942350332594%\" valign=\"top\"\u003e\n \u003cp\u003e0.84, 4.79\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"46.11973392461197%\" valign=\"top\"\u003e\n \u003cp\u003eEducation*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.620842572062084%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.25942350332594%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"46.11973392461197%\" valign=\"top\"\u003e\n \u003cp\u003eObligatory schooling\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.620842572062084%\" valign=\"top\"\u003e\n \u003cp\u003e4.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.25942350332594%\" valign=\"top\"\u003e\n \u003cp\u003e0.91, 17.39\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"46.11973392461197%\" valign=\"top\"\u003e\n \u003cp\u003eVocational\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.620842572062084%\" valign=\"top\"\u003e\n \u003cp\u003e1.15\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.25942350332594%\" valign=\"top\"\u003e\n \u003cp\u003e0.48, 2.68\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"46.11973392461197%\" valign=\"top\"\u003e\n \u003cp\u003eMatura\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.620842572062084%\" valign=\"top\"\u003e\n \u003cp\u003e1.23\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.25942350332594%\" valign=\"top\"\u003e\n \u003cp\u003e0.33, 3.66\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"46.11973392461197%\" valign=\"top\"\u003e\n \u003cp\u003eHigher technical degree\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.620842572062084%\" valign=\"top\"\u003e\n \u003cp\u003e0.93\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.25942350332594%\" valign=\"top\"\u003e\n \u003cp\u003e0.38, 2.15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe odds ratios in bold are those significantly associated with the odds of having a health event that day (95% confidence interval does not cross the null value of 1).\u003c/p\u003e\n\u003cp\u003e*Comparison group: those who completed a university degree or higher.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eOur study provides evidence that the risk of COVID-19 seropositivity among those taking PrEP was higher than in the general population in Zurich in the first wave of the COVID-19 pandemic in Switzerland. This risk did not appear to be associated with the number of sexual partners that SwissPrEPared participants reported during the first lockdown, however; in fact, 33% of seropositive participants did not report having any sexual contacts at all. This, linked with the finding that social contacts during the first wave of the pandemic were counterintuitively lower among those who were seropositive, suggests that sexual behaviors were not strongly linked with COVID-19 seropositivity during this time period. Those who were seropositive were more likely to be living alone and less likely to have ever received a flu vaccination, but the risk factor investigated in this study that was most robustly linked with SARS-CoV-2 seropositivity in both the general population and the SwissPrEPared population was the number of trips abroad during the pandemic.\u003c/p\u003e \u003cp\u003eWhile sexual behavior did not appear to be linked with increased risk of SARS-CoV-2 seropositivity within the SwissPrEPared population during the first pandemic wave, there was still a 46% increased risk of infection with SARS-CoV-2 compared with the general male Corona Immunitas population in Zurich after propensity score matching for age, travel, household size, and education. The population of SwissPrEPared participants differs in important ways with that of the general male population from Corona Immunitas (younger, more highly educated, more often living alone, travel more frequently). It may be that other, unmeasured factors account for this increased risk. It is well known that cluster infections (e.g. within family or friend groups) played an important role in the early transmission of COVID-19,\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e meaning that the risk is not particularly linked to individual characteristics, but instead social group membership.\u003c/p\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eDifferences in SARS-COV-2 seropositivity between the cohort taking PrEP and the general population\u003c/h2\u003e \u003cp\u003eThe study shows that the prevalence of SARS-CoV-2 infection among participants taking PrEP in Zurich was higher than that of the general Zurich male population from the Corona Immunitas study (prevalence 8.7% vs 5.5%) during the first pandemic wave. This increased risk persists even after propensity score matching the two populations on some key characteristics, such as age, education, household size, and international travel, although the difference in absolute terms is not large. As is true in other cohorts of people taking PrEP,\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e there are key demographic differences between this group and the general population. Although we were able to match the two populations based on these five key characteristics, we were not able to match on other key demographic characteristics that may also have been related to risk of COVID-19 transmission (e.g. profession and occupational exposures, pre-existing health conditions).\u003csup\u003e\u003cspan additionalcitationids=\"CR36\" citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eHealth and sexual behaviors and COVID-19 transmission in the cohort taking PrEP\u003c/h2\u003e \u003cp\u003eParticipants taking PrEP who were seropositive for SARS-CoV-2 differed in some key health behaviors and attitudes. Lifetime flu vaccine uptake was higher in the seronegative group (49% vs 38%), which may translate to their risk attitude and other health behaviors regarding infectious disease in general, known as the healthy vaccine effect.\u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e Other studies have also found that those who were previously vaccinated against the flu had decreased risk of COVID-19 infection.\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e These participants may also have been more likely to take protective measures against other infectious diseases, resulting in lower levels of exposure to COVID-19. Seropositive participants were more likely to be living alone. While it is well established that the pandemic had adverse effects on the mental health of those living alone,\u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e there is less evidence on how living alone affected COVID-19 transmission and choices around protective behavior. However, a meta-analysis on household transmission found that counterintuitively those living in households with three or more contacts had higher secondary attack rates than those living in households with only one contact.\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e More studies are needed. The behavioral finding most robustly associated with increased risk of COVID-19 seropositivity is travel abroad. The important role of travel abroad in infection and transmission of COVID-19 in the early stages of the pandemic has been established in other studies.\u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e,\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eSwissPrEPared participants showed high compliance with social distancing measures. This high level of compliance was similar among both the seropositive and the seronegative. The overwhelming majority of study participants (94%) also later received the COVID-19 vaccination. The results of this study also indicate that SwissPrEPared participants reduced their sexual contacts during the pandemic, similar to what was reported in the United States, Israel, Brazil, and Australia\u003csup\u003e\u003cspan additionalcitationids=\"CR6 CR7\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. This contrasts with what was found in a 2021 German study of PrEP users, which found no change in sexual behavior compared to pre-pandemic, but a similar rate of seroconversion as that of the general population.\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e Other studies from the United States that recruited through dating applications suggested that MSM did not change their sexual behavior or even increased the number of sexual partners during the pandemic, but that may reflect that these populations were recruited from those actively on dating applications during the pandemic.\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e Another study from the US found age related differences in sexual behavior during the pandemic, with younger MSM having large decreases in testing and PrEP use, but only small reductions in numbers of sexual partners.\u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eIt is surprising that reported levels of social contacts were lower among the seropositive compared with the before, during, and after the pandemic. It may have been that these participants were able to safely create opportunities to socialize and/or engage in sexual activities while only minimally increasing transmission risk (e.g. through creating \u0026ldquo;pods\u0026rdquo;). It is also possible that these data reflect a reporting bias; i.e., that participants that were aware that they had had COVID-19 underreported their social contacts during the pandemic. However, seropositive participants also reported fewer numbers of sexual partners during the study period (median 3.8 vs. 5.0). Since these numbers were reported in real time during the pandemic and most likely prior to knowledge of COVID-19 status, it is unlikely that they were affected by reporting bias. Finally, it may be that those who were symptomatic may have been more likely to isolate after their symptomatic episode, or during specific time periods during the pandemic. Future studies on these behavioral aspects of sexual health could incorporate qualitative research to better understand these findings.\u003c/p\u003e \u003cp\u003eThe lack of association of education and other sociodemographic characteristics with seropositivity is similar to what was found in the overall Swiss population in the first wave of the pandemic, where only younger age was associated with increased seropositivity.\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e This may reflect high compliance with overall social distancing measures during the initial phases of the pandemic in Switzerland.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eLimitations\u003c/h2\u003e \u003cp\u003eThis study is subject to some limitations. Participants in this study were those that did not discontinue use of PrEP during the initial pandemic lockdown, meaning that they are likely less risk averse than participants that did stop attending their PrEP visits during this time. The number of people who were seropositive in this cohort was small (n\u0026thinsp;=\u0026thinsp;19), meaning that the data on behavioral and demographic patterns in seropositivity need to be interpreted with caution. In addition, similar information on sexual behaviors during the lockdown was not available for sexually active individuals not on PrEP during this time period, so it is not possible to compare this group with other sexually active groups (e.g. heterosexuals). As mentioned above, there is a possibility of reporting bias, with those who had symptoms of COVID-19 remembering being more cautious than they really were. However, data on sexual behavior was reported as part of routine PrEP follow-up visits, making it unlikely that underreporting is linked to COVID-19 status. Finally, there was likely residual confounding in the comparison between the cohort of people taking PrEP and the general male population in Zurich.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eOverall, COVID-19 seropositivity during the first pandemic wave was slightly elevated in a cohort of people taking PrEP compared to the general male population in Zurich, Switzerland. Our study suggests that at least in the first wave of lockdown, socializing and sexual activity were less important than other factors in COVID-19 seropositivity among those taking PrEP. While we cannot retrospectively identify precisely what those factors were, the association of seropositivity with international travel and deprioritization of health protection measures such as vaccination suggest that these factors may have played a role. Those who were less likely to prioritize precautionary measures such as vaccines may also have been less likely to prioritize complying with social distancing measures.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThis study is part of Corona Immunitas research network, coordinated by the Swiss School of Public Health (SSPH+), and funded by fundraising of SSPH+\u0026nbsp;including funds of the Swiss Federal Office of Public Health and private funders (ethical guidelines for funding stated by SSPH+\u0026nbsp;were respected). Financial support from the Swiss Federal Office of Public Health (FOPH) was received by the SwissPrEPared program and study. The funding bodies had no influence on the design, conduct, analysis or interpretation of the study, nor on the decision to publish, the preparation or revisions of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eEthics Approval \u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThis study was performed in line with the principles of the Declaration of Helsinki. The SwissPrEPared study (NCT03893188) was approved by the lead ethical committee (EC) in Zurich on 14 May 2019 (BASEC Nr. 2018-02015), followed by the approval of all ECs from the other cantons. The Corona Immunitas study was approved by the lead EC in Zurich (BASEC Nr. 2020-01247), followed by the approval of all ECs from the other cantons.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eConsent\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eInformed consent was obtained from all individual participants included in the study.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eDe-identified individual participant data underlying the findings and the codes used for this study will be available for researchers. Requests can be made to the Executive Committee of Corona Immunitas [https://zenodo.org/record/7520125] or to the corresponding author.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization: Benjamin Hampel, Anja Frei, Andrea Farnham; Methodology: Benjamin Hampel, Anja Frei, Matthias Reinacher, Milo A. Puhan, Jan S. Fehr, ; Formal analysis and investigation: Andrea Farnham; Writing - original draft preparation: Andrea Farnham; Writing - review and editing: Benjamin Hampel, Julia Kopp, Larissa J. Schori, Olivia J. Kotoun, Matthias Reinacher, Manuela Rasi, Milo A. Puhan, Jan S. Fehr; Funding acquisition: Benjamin Hampel, Milo A. Puhan, Jan S. Fehr; Supervision: Benjamin Hampel, Anja Frei, Jan S. Fehr, Milo A. Puhan\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to thank the participants in the study for their time and and contributions to the study, as well as the study administrative staff for their dedicated support of the study.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eWinter BL, Hovaguimian F, Kouyos RD, \u003cem\u003eet al.\u003c/em\u003e Changes in mental and sexual health among MSM using HIV pre-exposure prophylaxis during the SARS-CoV-2 pandemic: longitudinal analysis of the SwissPrEPared cohort study. \u003cem\u003eSwiss Med Wkly\u003c/em\u003e 2022; \u003cstrong\u003e152\u003c/strong\u003e: w30192.\u003c/li\u003e\n \u003cli\u003eBzdok D, Dunbar RIM. 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However, it remains unclear whether sexual contact with non-steady partners was a contributor to the spread of SARS-CoV-2. The aim of this study was to (i) assess whether the SARS-CoV-2 seropositivity after the first pandemic wave among people using HIV Pre-Exposure Prophylaxis (PrEP) in Zurich, Switzerland differed from that of a demographic matched population level comparison group, (ii) describe risk factors for SARS-CoV-2 seropositivity in this population, and (iii) determine whether sexual contact with non-steady partners was associated with SARS-CoV-2 seropositivity.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was conducted between July 2020 and October 2020 as a nested cross-sectional study within two ongoing cohort studies, SwissPrEPared (all eligible PrEP users in Switzerland ≥18 years old) and Corona Immunitas (a series of cross-sectional and longitudinal studies measuring the SARS-CoV-2 seroprevalence across Switzerland, beginning in April 2020). All SwissPrEPared participants were recruited from Checkpoint Zurich (the main PrEP clinic in Zurich). Data were collected on participants’ SARS-CoV-2 antibody status, social characteristics and behavioral data after the first wave of the corona pandemic in Switzerland, and seroprevalence was compared with a propensity score-matched sample from the general Zurich population.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOf the 218 participants enrolled, 8.7% (n=19, 95% CI: 5.5-13.5%) were seropositive for SARS-CoV-2 during the first pandemic wave, higher than that of the general male population in Zurich aged 20-65 (5.5%, 95% CI: 3.8–8.2%). Participants on average reduced their social outings, but the seronegative were more socially active before, during, and after the first lockdown period. In a logistic model, increasing mean sexual partner count was not associated with seropositivity (OR: 0.9, 95% CI: 0.8, 1.0), but increasing number of trips abroad was associated with higher seropositivity (p=0.06, OR: 1.14, 95% CI: 1.0, 1.3). The estimated risk ratio for seropositivity for the participants compared to the general Zurich population after propensity score matching was 1.5 (95% CI: 0.53, 4.0). 94% of participants reported later receiving a COVID-19 vaccination.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDiscussion:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOur study suggests that COVID-19 seropositivity was slightly elevated among people taking PrEP in Zurich during the first wave of the pandemic, but that socializing and sexual activity were less important than other factors in contributing to risk.\u003c/p\u003e","manuscriptTitle":"Sexual behaviours among MSM during the first COVID-19 lockdown not associated with risk of COVID-19 infection","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-03 17:21:01","doi":"10.21203/rs.3.rs-4169289/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-09-12T08:37:52+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-07-26T14:56:07+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"20543165283299612214317931816825396844","date":"2024-07-22T15:44:03+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-06-21T17:21:49+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"117233642906753886877606425924896077893","date":"2024-05-29T09:31:50+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-05-27T09:22:39+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2024-04-01T07:03:35+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-03-29T11:47:00+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-03-29T11:46:59+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Public Health","date":"2024-03-26T10:57:36+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-public-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pubh","sideBox":"Learn more about [BMC Public Health](http://bmcpublichealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/pubh/default.aspx","title":"BMC Public Health","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f68ac940-2c10-41d6-aea9-7793287c909e","owner":[],"postedDate":"April 3rd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-11-04T16:28:41+00:00","versionOfRecord":{"articleIdentity":"rs-4169289","link":"https://doi.org/10.1186/s12889-024-20514-9","journal":{"identity":"bmc-public-health","isVorOnly":false,"title":"BMC Public Health"},"publishedOn":"2024-11-02 16:20:29","publishedOnDateReadable":"November 2nd, 2024"},"versionCreatedAt":"2024-04-03 17:21:01","video":"","vorDoi":"10.1186/s12889-024-20514-9","vorDoiUrl":"https://doi.org/10.1186/s12889-024-20514-9","workflowStages":[]},"version":"v1","identity":"rs-4169289","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4169289","identity":"rs-4169289","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}