Effectiveness of COVID-19 vaccination in breastfeeding women in preventing SARS-CoV-2 infection in infants

Effectiveness of COVID-19 vaccination in breastfeeding women in preventing SARS-CoV-2 infection in infants | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Effectiveness of COVID-19 vaccination in breastfeeding women in preventing SARS-CoV-2 infection in infants Kamolwish Laoprasopwattana, Nattaporn Tassanakijpanich, Puttichart Khantee, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4780196/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objective: To compare the COVID-19 transmission rates between infants who were primarily breastfed and those formula fed in mothers who received at least 2 doses of the COVID-19 vaccines. Methods: A prospective longitudinal study was conducted during the Omicron wave (January 1-October 1, 2022). Infants who exhibited respiratory symptoms were tested for SARS-CoV-2 by RT-PCR. Results: Of 234 infants, 66 (28.2%) tested positive for SARS-CoV-2, with 63 out of the 66 (95.5%) having a mother with COVID-19, and a median (IQR) age at diagnosis of 11.3 (10.8-11.9) months. The proportions of COVID-19 in 6- and 12-month breastfed and formula fed dominant infants were 27.0% vs. 31.0%, p =0.53 and 21.1% vs. 31.3%, p =0.11, respectively. In the multivariate Cox regression models, both 6- and 12-month breastfed only/dominant infants had a protected effect against COVID-19 with hazard ratios (HRs, 95% CI) of 1.50 (0.90, 2.51), p =0.13 and 1.63 (0.90, 2.51), p =0.09, respectively. Maternal vaccine regimens had no protective effect against COVID-19 with the HR of 0.86 (0.49, 1.52), p =0.61. In sub-group analysis, infants with a mother that had received 2 doses within 6 months and were breastfed only/dominant at 12 months had a protected effect against COVID-19 with the HR of 3.77 (0.77, 18.43), p =0.05. Conclusion : Mothers who have experienced COVID-19 can nurse without increasing the risk of SARS-CoV-2 transmission. Despite the possibility that breastfeeding mothers who receive the COVID-19 vaccine can shield their infants from the virus, the statistical evidence is insignificant. SARS-CoV-2 COVID-19 breastfeeding vaccine infants Figures Figure 1 Introduction Coronavirus disease 2019 (COVID-19) affected billions of people globally after it was declared a pandemic by the World Health Organization (WHO) on March 11, 2020. 1 Among the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants, the Omicron variant and its outbreak in Thailand during January-September 2022 caused symptomatic infections in young children in a higher proportion than in other age groups. 2 In Thailand, the Ministry of Public Health downgraded COVID-19 from a dangerous communicable disease to an endemic disease for which active surveillance was not needed on 1st October 2022. Children being more vulnerable to Omicron could be explained by the Omicron variant’s extremely high transmissibility and a lack of built-up immunity from vaccinations or past infections. In Thailand, a policy of COVID-19 vaccinations for children aged six months to five years was implemented in October 2022. Previous studies found that SARS-CoV-2 was found in breast milk. 3 , 4 Anti-SARS-CoV-2 antibodies were also found in breast milk following both natural SARS-CoV-2 infection and COVID-19 vaccinations, which could potentially provide protection for very young children. 5 – 10 Previous studies in lactating women who were vaccinated with 2 doses of a COVID-19 mRNA vaccine found SARS-CoV-2 IgG in the breast milk 7 , 8 , 11 with a high correlation with SARS-CoV-2 IgG levels in the serum (Pearson correlation 0.7). 11 In Thailand, due to limited vaccine supplies and/or concerns about the side effects of the mRNA vaccines such as BNT162b2 and mRNA-1273, alternative vaccine strategies such as heterologous regimens, CoronaVac-ChAdOx1, CoronaVac-BNT162b2, and ChAdOx1- BNT162b2 were implemented to improve vaccine coverage. These regimens have been found to be safe and capable of inducing similar or higher humoral and cellular immune responses than the homologous BNT162b2-BNT162b2 vaccinations in both children and adults. 12 , 13 The objective of this study was to compare the COVID-19 transmission rates between infants who were breastfed-dominant and formula fed-dominant in mothers who had received at least 2 doses of the COVID-19 vaccines before their child was one year old. Methods A prospective longitudinal study was conducted during the Omicron wave of the COVID-19 pandemic, from January 1, 2022, to October 1, 2022, at the outpatient pediatric clinic of Songklanagarind Hospital, the major tertiary hospital in southern Thailand. The study included 234 healthy infants whose mothers had received at least 2 doses of COVID-19 vaccines before the child was one year old. Children who had COVID-19 prior to the beginning of the study period were excluded. During the study period, if an infant exhibited respiratory symptoms such as fever, cough, runny nose, and/or difficulty breathing, the mother was asked to bring the infant to Songklanagarind Hospital. If a family member had a current COVID-19 infection, the infant would undergo RT-PCR testing for SARS-CoV-2. Demographic information of the patients was collected, including breastfeeding status at 6 and 12 months, date of contraction of mothers and infants who contracted COVID-19 during the study period, and type of COVID-19 vaccine used and dates of vaccinations for the mothers. The mothers’ vaccinations were classified into 2 regimens: 1) an mRNA regimen, which was defined as a regimen containing at least one mRNA vaccine as a second dose after the first dose of one of Sinovac/Sinopharm or AstraZeneca, and 2) a ‘no mRNA’ regimen, defined as two doses of any of the non-mRNA vaccines. During the study period, the mothers were asked about their infant’s feeding habits at 6 and 12 months of age and were recorded as either primarily breastfed or formula fed. Infants who consumed more breast milk than formula milk during the first six months and 12 months of life were categorized as breastfed dominant, while infants who consumed more formula milk than breast milk were classified as formula dominant. Statistical analysis All data were managed and analyzed using the R program version 4.2.3. Descriptive statistics were used to summarize all variables. The primary outcome variable of this study was COVID-19 status of the enrolled infants, while the exposure variables were breastfeeding status at 6 and 12 months and maternal vaccine regimen. Median and interquartile range (IQR) were used to describe continuous variables based on their distribution, while the categorical variables were summarized using frequency and percentage. In univariate analysis, the Mann–Whitney U test and chi-squared test were performed for association testing for continuous and categorical variable, respectively. To estimate the hazard ratios of COVID-19 in children in relation to the mother’s vaccination status and their breastfeeding status, survival analyses were conducted using Kaplan-Meier curves and Cox regression models. After adjusting for potential confounding variables, sub-group analysis was also performed for infants with mothers that had received 2 doses of vaccine within 6 months following childbirth. 7 , 8 , 11 The significance levels (α) for the univariate and multivariate analyses were 0.2 and 0.05, respectively. Ethics approval The study was approved by the Institutional Review Board of the Faculty of Medicine, Prince of Songkla University (REC 65-066-2) and was conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained from a legally authorization representative. This research was financially supported by the Faculty of Medicine, Prince of Songkla University Results Clinical characteristics of study infants During the 9-month study period, 66 out of 234 infants (28.2%) contracted COVID-19, with 63 out of the 66 (95.5%) having a mother with confirmed COVID-19, and a median (IQR) age at diagnosis of 11.3 (10.8-11.9) months. The median ages of the infants at the time their mothers received the initial and subsequent doses of the COVID-19 vaccine were 5.6 and 6.7 months, respectively. The breastfed only/dominant group at the ages of 6-months and 12-months were 69.6% and 30.3%, respectively. The proportions of COVID-19 in the 6-month breastfed and formula fed dominant infants were 44/163 (27.0%) and 22/71 (31.0%), respectively, p =0.53. The proportions of COVID-19 in the 12-month breastfed and formula fed dominant infants were 21.1% and 31.3%, respectively, p =0.11. All of the infants who contracted COVID-19 had mild to moderate symptoms. None of them had severe pneumonia nor respiratory failure and all were alive and healthy at the end of the study period. Comparison of the clinical characteristics of the study infants who contracted and did not contract COVID-19 The proportion of mothers who had a history of COVID-19 during study period was significantly higher in the infants who contracted COVID-19 (95.5%) when compared to infants who did not contract COVID-19 (41.7%). None of the mothers who contracted COVID-19 during the study period had severe illness. The medians (IQR) of age at beginning of the study (1 st January 2022) and average child’s age at the 1 st and 2 nd maternal immunizations were not significantly different between the infants who developed or did not develop COVID-19 during the study period (Table 1). The proportions of male gender, breast feeding status at 6 months and 12 months, maternal vaccine regimens with and without mRNA, and mothers vaccinated within 6 months following birth of the study infants were not significantly different between the infants who developed or did not develop COVID-19 (Table 1). Impact of breastfeeding status and immunization regimens on COVID-19 Although the COVID-19 negative probability curves of breastfed only/dominant infants at both 6 months and 12 months of age were higher compared with the formula-dominant infants, the confidence intervals of the curves overlapped with those of the formula dominant infants (Fig. 1A-B). There were no noticeable differences in the COVID-19 negative probability curves stratified by maternal vaccine regimens (Fig. 1C). In the multivariate Cox regression models, after adjusting for the covariates, the hazard ratios supported the results of the Kaplan-Meier curves. In all infants, at both 6 and 12 months breastfed only/dominant had a protective effect against COVID-19 that approached statistical significance with the hazard ratio (HR) and 95% confidence interval (CI) of 1.50 (0.90, 2.51), p =0.13 and 1.63 (0.90, 2.51), p =0.09, respectively. Maternal vaccine regimen had no protective effect against COVID-19 with an HR (95% CI) of 0.86 (0.49, 1.52) p =0.61 (Table 2). The sub-group results of the Cox regression analysis regarding vaccine regimen were omitted, as all 3 infants whose mothers had received one or more mRNA vaccinations within 6 months remained COVID-19 negative throughout the study period. Infants with a mother that received 2 doses within 6 months, breastfed only/dominant at 12 months had a protective effect against COVID-19 with the HR (95%CI) of 3.77 (0.77, 18.43), p =0.053 (Table 2). Discussion The COVID-19 rates in breastfed only/dominant infants until 6 and 12 months of age were not statistically different from the formula dominant infants, nor were the rates different between infants whose mothers had received an mRNA-containing or no-mRNA-containing vaccine regimen. In this study, only 36.7% of the mothers had received at least 2 doses of COVID-19 vaccines by the time their infants reached the age of six months, and the median ages of the children whose mothers had the second dose of their vaccine in infants who contracted or did not contract COVID-19 during the study period were 6.5 and 6.8 months, respectively (Table 1). These findings explain why the rate of COVID-19 in the breastfed only/dominant until the age of six months group was comparable to that of the other group throughout the study period. Although we found a protective effect against COVID-19 with the adjusted HR of 1.63 (P = 0.09) in the breastfed only/dominant group until the age 12 months, and whose mothers had completed two doses of vaccine before the infants were 6 months of age with an adjusted HR of 3.77 (P = 0.05), the protective effect was not statistically significant. Antibodies to SARS-CoV2 have been identified in the breast milk of mRNA-vaccinated mothers 11,14,15 , but to the best of our knowledge, no study to date has examined the benefit of a non-mRNA vaccine-recipient mother in the mother’s breast milk in preventing infants from contracting COVID-19. Our findings suggest that mothers receiving non-mRNA vaccines might be as beneficial in preventing infants from contracting COVID-19 as mRNA vaccines, since the majority of mothers with a completed COVID-19 vaccination regimen prior to their infants reaching the age of 6 months had received non-mRNA vaccines. The study had several limitations: firstly, there was a limited number of infants whose mothers had received complete COVID-19 vaccination regimens before the infants reached 6 months of age; secondly, there was a very limited number of mothers who had received an mRNA vaccine before their infants reached the age of 6 months, making it impossible to compare the efficacy between these two vaccine groups; and finally, none of the infants were exclusively fed formula milk so the infants might have gotten some passive antibodies from their breast milk. We found that the breast milk of mothers who have received the COVID-19 vaccination may help shield their infants from the virus, and that mothers who have had COVID-19 can nurse without raising the risk of SARS-CoV-2 transmission to the infants. Nevertheless, the results were not statistically significant due to the limited number of sample sizes. To draw a conclusion regarding these findings, additional research is required. Declarations Role of the Funder/Sponsor: The funding organization had no role in the design or conducting of the study; the collection, management, analysis, and interpretation of the data; the preparation, review, or approval of the manuscript; or the decision to submit the manuscript for publication. Acknowledgements The authors wish to thank Kemmapon Chumchuen for assistance with data analysis, and David Patterson, an English teacher and writing consultant, for help with the English, both of whom work with the Faculty of Medicine, Prince of Songkla University. We received permission from Merck Sharp & Dohme LLC to collect data from the participants of the V114-032/PNEU-ERA research study at Site 0005 (NCT04193215). Author Contribution K.L. wrote the main manuscript text; N.T, P.K, S.K, P.R, and V .K gathered information and performed data entry. All authors reviewed the manuscript." References WHO. COVID-19. [accessed 2023 Apr 1]. https://covid19.who.int/ . Worldometer. COVID-19 coronavirus pandemic. 2019. [accessed 2023 Apr 1]. https://www.worldometers.info/coronavirus/ . Gross R, Conzelmann C, Muller JA, et al. Detection of SARS-CoV-2 in human breastmilk. Lancet. 2020;395:1757–8. Murano Y, Yamahira S, Shoji H, et al. Evaluation of the transmission of SARS-CoV-2 through breast milk: a case series. Front Pediatr. 2023;11:1160790. Peng S, Zhu H, Yang L, et al. A study of breastfeeding practices, SARS-CoV-2 and its antibodies in the breast milk of mothers confirmed with COVID-19. Lancet Reg Health West Pac. 2020;4:100045. Bauerl C, Randazzo W, Sanchez G, et al. SARS-CoV-2 RNA and antibody detection in breast milk from a prospective multicentre study in Spain. Arch Dis Child Fetal Neonatal Ed. 2022;107:216–21. Esteve-Palau E, Gonzalez-Cuevas A, Guerrero ME, et al. Quantification and progress over time of specific antibodies against severe acute respiratory syndrome coronavirus 2 in breast milk of lactating women vaccinated with BNT162b2 Pfizer-BioNTech Coronavirus Disease 2019 Vaccine (LacCOVID). Open Forum Infect Dis. 2022;9:ofac239. Duncombe CJ, McCulloch DJ, Shuey KD, et al. Dynamics of breast milk antibody titer in the six months following SARS-CoV-2 infection. J Clin Virol. 2021;142:104916. Bauerl C, Zulaica J, Rusu L, et al. Assessment of SARS-CoV-2 neutralizing antibody titers in breastmilk from convalescent and vaccinated mothers. iScience. 2023;26:106802. Juncker HG, Mulleners SJ, van Gils MJ et al. Comparison of SARS-CoV-2-specific Antibodies in Human Milk after mRNA-Based COVID-19 Vaccination and Infection. Vaccines (Basel) 2021; 9(12). Esteve-Palau E, Gonzalez-Cuevas A, Guerrero ME, et al. Quantification of specific antibodies against SARS-CoV-2 in breast milk of lactating women vaccinated with an mRNA vaccine. JAMA Netw Open. 2021;4:e2120575. Wittawatmongkol O, Bunjoungmanee P, Kosalaraksa P, et al. Immunogenicity and reactogenicity of fractional, heterologous primary COVID-19 vaccination schedules with BNT162b2 boosters in 5-11-year-old Thai children: A multicenter, prospective, double-blind, randomized control trial. Vaccine. 2023;41:5834–40. Niyomnaitham S, Toh ZQ, Wongprompitak P, et al. Immunogenicity and reactogenicity against the SARS-CoV-2 variants following heterologous primary series involving CoronaVac and ChAdOx1 and BNT162b2 plus heterologous BNT162b2 booster vaccination: An open-label randomized study in healthy Thai adults. Hum Vaccin Immunother. 2022;18:2091865. Narayanaswamy V, Pentecost BT, Schoen CN, et al. Neutralizing Antibodies and Cytokines in Breast Milk After Coronavirus Disease 2019 (COVID-19) mRNA Vaccination. Obstet Gynecol. 2022;139:181–91. Calvo-Lerma J, Bueno-Llamoga P, Bauerl C, et al. Persistence of Anti SARS-CoV-2 antibodies in breast milk from infected and vaccinated women after in vitro-simulated gastrointestinal digestion. Nutrients. 2022;14:2117. Tables Tables 1 to 2 are available in the Supplementary Files section Additional Declarations No competing interests reported. Supplementary Files Table1.docx Table2.docx Cite Share Download PDF Status: Posted Version 1 posted 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. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-4780196","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":339376500,"identity":"e3eafd72-4a7c-414d-a357-670e2f2aaad9","order_by":0,"name":"Kamolwish Laoprasopwattana","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA1UlEQVRIiWNgGAWjYBACCRDxAEgZsDcAWQYWRGpJAGnhOQDSIkG0FpDiBDgfP5BsP534ILHNwt5c8vnVDT8KJBj427sT8GqR5sndbJDYJpG4c3ZO2c0eoMMkzpzdgFeLHEPuNonEbRIJBrdz0m7wALUYSOQS0ML/FqzF3uDmmbSbf4jRIi0BsYVxww32Y7eJskVyxlugX/5JJG44k8N2W8ZAgoegXyTO52588OFMnb3B8ePPbr75YyPH396LXwsS4DEAk8QqBwH2B6SoHgWjYBSMghEEABRSSCDhpER1AAAAAElFTkSuQmCC","orcid":"","institution":"Prince of Songkla University","correspondingAuthor":true,"prefix":"","firstName":"Kamolwish","middleName":"","lastName":"Laoprasopwattana","suffix":""},{"id":339376506,"identity":"3056e1e4-280a-4708-94c7-4bcf7e30ba54","order_by":1,"name":"Nattaporn Tassanakijpanich","email":"","orcid":"","institution":"Prince of Songkla University","correspondingAuthor":false,"prefix":"","firstName":"Nattaporn","middleName":"","lastName":"Tassanakijpanich","suffix":""},{"id":339376510,"identity":"e576908d-5b4e-4356-95d0-ff1b91eaf0b8","order_by":2,"name":"Puttichart Khantee","email":"","orcid":"","institution":"Prince of Songkla University","correspondingAuthor":false,"prefix":"","firstName":"Puttichart","middleName":"","lastName":"Khantee","suffix":""},{"id":339376513,"identity":"295aee5b-5eb8-42b7-bf76-13d380e25696","order_by":3,"name":"Sirinthip Kittivisuit","email":"","orcid":"","institution":"Prince of Songkla University","correspondingAuthor":false,"prefix":"","firstName":"Sirinthip","middleName":"","lastName":"Kittivisuit","suffix":""},{"id":339376514,"identity":"3ddfeb26-6f7a-4f5c-9419-37355a6b3bb4","order_by":4,"name":"Pornruedee Rachatawiriyakul","email":"","orcid":"","institution":"Prince of Songkla University","correspondingAuthor":false,"prefix":"","firstName":"Pornruedee","middleName":"","lastName":"Rachatawiriyakul","suffix":""},{"id":339376516,"identity":"da297989-c569-4c9e-9c74-5480a6e73ff7","order_by":5,"name":"Vanlaya Koosakulchai","email":"","orcid":"","institution":"Prince of Songkla University","correspondingAuthor":false,"prefix":"","firstName":"Vanlaya","middleName":"","lastName":"Koosakulchai","suffix":""}],"badges":[],"createdAt":"2024-07-22 08:12:56","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4780196/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4780196/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":63313586,"identity":"5d08bfc8-4e33-4c0d-bcca-c9ac2ad933cc","added_by":"auto","created_at":"2024-08-26 20:57:50","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":113524,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA-C. \u003c/strong\u003eKaplan-Meier curves for remaining COVID-19 negative. A) stratified by breastfeeding status at 6 months B) stratified by breastfeeding status at 12 months C) stratified by maternal vaccine regimen.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4780196/v1/06c8ece41a87da04bd8209e1.png"},{"id":79870959,"identity":"3029c335-96a8-4963-9356-b1d47192f364","added_by":"auto","created_at":"2025-04-03 21:46:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":555898,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4780196/v1/fd8c2833-91b8-405c-96b7-497c6c1b3bb1.pdf"},{"id":63313123,"identity":"175f0d19-f963-4c6e-8a1b-afe9d7e445e2","added_by":"auto","created_at":"2024-08-26 20:49:50","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":17756,"visible":true,"origin":"","legend":"","description":"","filename":"Table1.docx","url":"https://assets-eu.researchsquare.com/files/rs-4780196/v1/2d0368d27bfda5213b4890fe.docx"},{"id":63313122,"identity":"d6522980-c912-40f6-8a20-2556a9c8cdd0","added_by":"auto","created_at":"2024-08-26 20:49:50","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":16303,"visible":true,"origin":"","legend":"","description":"","filename":"Table2.docx","url":"https://assets-eu.researchsquare.com/files/rs-4780196/v1/dd27e8fe161e1afc39dc7bdd.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effectiveness of COVID-19 vaccination in breastfeeding women in preventing SARS-CoV-2 infection in infants","fulltext":[{"header":"Introduction","content":"\u003cp\u003eCoronavirus disease 2019 (COVID-19) affected billions of people globally after it was declared a pandemic by the World Health Organization (WHO) on March 11, 2020.\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e Among the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants, the Omicron variant and its outbreak in Thailand during January-September 2022 caused symptomatic infections in young children in a higher proportion than in other age groups.\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e In Thailand, the Ministry of Public Health downgraded COVID-19 from a dangerous communicable disease to an endemic disease for which active surveillance was not needed on 1st October 2022.\u003c/p\u003e \u003cp\u003eChildren being more vulnerable to Omicron could be explained by the Omicron variant\u0026rsquo;s extremely high transmissibility and a lack of built-up immunity from vaccinations or past infections. In Thailand, a policy of COVID-19 vaccinations for children aged six months to five years was implemented in October 2022. Previous studies found that SARS-CoV-2 was found in breast milk. \u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e Anti-SARS-CoV-2 antibodies were also found in breast milk following both natural SARS-CoV-2 infection and COVID-19 vaccinations, which could potentially provide protection for very young children.\u003csup\u003e\u003cspan additionalcitationids=\"CR6 CR7 CR8 CR9\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e Previous studies in lactating women who were vaccinated with 2 doses of a COVID-19 mRNA vaccine found SARS-CoV-2 IgG in the breast milk\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e with a high correlation with SARS-CoV-2 IgG levels in the serum (Pearson correlation 0.7).\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eIn Thailand, due to limited vaccine supplies and/or concerns about the side effects of the mRNA vaccines such as BNT162b2 and mRNA-1273, alternative vaccine strategies such as heterologous regimens, CoronaVac-ChAdOx1, CoronaVac-BNT162b2, and ChAdOx1- BNT162b2 were implemented to improve vaccine coverage. These regimens have been found to be safe and capable of inducing similar or higher humoral and cellular immune responses than the homologous BNT162b2-BNT162b2 vaccinations in both children and adults.\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eThe objective of this study was to compare the COVID-19 transmission rates between infants who were breastfed-dominant and formula fed-dominant in mothers who had received at least 2 doses of the COVID-19 vaccines before their child was one year old.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eA prospective longitudinal study was conducted during the Omicron wave of the COVID-19 pandemic, from January 1, 2022, to October 1, 2022, at the outpatient pediatric clinic of Songklanagarind Hospital, the major tertiary hospital in southern Thailand. The study included 234 healthy infants whose mothers had received at least 2 doses of COVID-19 vaccines before the child was one year old. Children who had COVID-19 prior to the beginning of the study period were excluded.\u003c/p\u003e \u003cp\u003eDuring the study period, if an infant exhibited respiratory symptoms such as fever, cough, runny nose, and/or difficulty breathing, the mother was asked to bring the infant to Songklanagarind Hospital. If a family member had a current COVID-19 infection, the infant would undergo RT-PCR testing for SARS-CoV-2.\u003c/p\u003e \u003cp\u003eDemographic information of the patients was collected, including breastfeeding status at 6 and 12 months, date of contraction of mothers and infants who contracted COVID-19 during the study period, and type of COVID-19 vaccine used and dates of vaccinations for the mothers.\u003c/p\u003e \u003cp\u003eThe mothers\u0026rsquo; vaccinations were classified into 2 regimens: 1) an mRNA regimen, which was defined as a regimen containing at least one mRNA vaccine as a second dose after the first dose of one of Sinovac/Sinopharm or AstraZeneca, and 2) a \u0026lsquo;no mRNA\u0026rsquo; regimen, defined as two doses of any of the non-mRNA vaccines.\u003c/p\u003e \u003cp\u003eDuring the study period, the mothers were asked about their infant\u0026rsquo;s feeding habits at 6 and 12 months of age and were recorded as either primarily breastfed or formula fed. Infants who consumed more breast milk than formula milk during the first six months and 12 months of life were categorized as breastfed dominant, while infants who consumed more formula milk than breast milk were classified as formula dominant.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eAll data were managed and analyzed using the R program version 4.2.3. Descriptive statistics were used to summarize all variables. The primary outcome variable of this study was COVID-19 status of the enrolled infants, while the exposure variables were breastfeeding status at 6 and 12 months and maternal vaccine regimen. Median and interquartile range (IQR) were used to describe continuous variables based on their distribution, while the categorical variables were summarized using frequency and percentage. In univariate analysis, the Mann\u0026ndash;Whitney U test and chi-squared test were performed for association testing for continuous and categorical variable, respectively. To estimate the hazard ratios of COVID-19 in children in relation to the mother\u0026rsquo;s vaccination status and their breastfeeding status, survival analyses were conducted using Kaplan-Meier curves and Cox regression models. After adjusting for potential confounding variables, sub-group analysis was also performed for infants with mothers that had received 2 doses of vaccine within 6 months following childbirth.\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e The significance levels (α) for the univariate and multivariate analyses were 0.2 and 0.05, respectively.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eEthics approval\u003c/h2\u003e \u003cp\u003e The study was approved by the Institutional Review Board of the Faculty of Medicine, Prince of Songkla University (REC 65-066-2) and was conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained from a legally authorization representative. This research was financially supported by the Faculty of Medicine, Prince of Songkla University\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003eClinical characteristics of study infants\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDuring the 9-month study period, 66 out of 234 infants (28.2%) contracted COVID-19, with 63 out of the 66 (95.5%) having a mother with confirmed COVID-19, and a median (IQR) age at diagnosis of 11.3 (10.8-11.9) months.\u0026nbsp;The median ages of the infants at the time their mothers received the initial and subsequent doses of the COVID-19 vaccine were 5.6 and 6.7 months, respectively.\u0026nbsp;The breastfed only/dominant group at the ages of 6-months and 12-months were 69.6% and 30.3%, respectively.\u003c/p\u003e\n\u003cp\u003eThe proportions of COVID-19 in the 6-month breastfed and formula fed dominant infants were 44/163 (27.0%) and 22/71 (31.0%), respectively, p =0.53. The proportions of COVID-19 in the 12-month breastfed and formula fed dominant infants were 21.1% and 31.3%, respectively, p =0.11.\u003c/p\u003e\n\u003cp\u003eAll of the infants who contracted COVID-19 had mild to moderate symptoms. None of them had severe pneumonia nor respiratory failure and all were alive and healthy at the end of the study period.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eComparison of the clinical characteristics of the study infants who contracted and did not contract COVID-19\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe proportion of mothers who had a history of COVID-19 during study period was significantly higher in the infants who contracted COVID-19 (95.5%) when compared to infants who did not contract COVID-19 (41.7%). None of the mothers who contracted COVID-19 during the study period had severe illness.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe medians (IQR) of age at beginning of the study\u0026nbsp;(1\u003csup\u003est\u003c/sup\u003e January 2022) and average\u0026nbsp;child’s age at the 1\u003csup\u003est\u003c/sup\u003e and 2\u003csup\u003end\u003c/sup\u003e maternal immunizations\u0026nbsp;were not significantly different between the infants who developed or did not develop COVID-19 during the study period (Table 1).\u003c/p\u003e\n\u003cp\u003eThe proportions of male gender, breast feeding status at 6 months and 12 months, maternal vaccine regimens with and without mRNA, and mothers vaccinated within 6 months following birth of the study infants were not significantly different between the infants who developed or did not develop COVID-19 (Table 1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eImpact of breastfeeding status and immunization regimens on COVID-19\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAlthough the COVID-19 negative probability curves of breastfed only/dominant infants at both 6 months and 12 months of age were higher compared with the formula-dominant infants, the confidence intervals of the curves overlapped with those of the formula dominant infants (Fig. 1A-B). There were no noticeable differences in the COVID-19 negative probability curves stratified by maternal vaccine regimens (Fig. 1C).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn the multivariate Cox regression models, after adjusting for the covariates, the hazard ratios supported the results of the Kaplan-Meier curves. In all infants, at both 6 and 12 months breastfed only/dominant had a protective effect against COVID-19 that approached statistical significance with the hazard ratio (HR) and 95% confidence interval (CI) of 1.50 (0.90, 2.51), p =0.13 and 1.63 (0.90, 2.51), p =0.09, respectively. Maternal vaccine regimen had no protective effect against COVID-19 with an HR (95% CI) of 0.86 (0.49, 1.52) p =0.61 (Table 2).\u003c/p\u003e\n\u003cp\u003eThe sub-group results of the Cox regression analysis regarding vaccine regimen were omitted, as all 3 infants whose mothers had received one or more mRNA vaccinations within 6 months remained COVID-19 negative throughout the study period. Infants with a mother that received 2 doses within 6 months, breastfed only/dominant at 12 months had a protective effect against COVID-19 with the HR (95%CI) of 3.77 (0.77, 18.43), p =0.053 (Table 2).\u0026nbsp;\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe COVID-19 rates in breastfed only/dominant infants until 6 and 12 months of age were not statistically different from the formula dominant infants, nor were the rates different between infants whose mothers had received an mRNA-containing or no-mRNA-containing vaccine regimen.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;In this study, only 36.7% of the mothers had received at least 2 doses of COVID-19 vaccines by the time their infants reached the age of six months, and the median ages of the children whose mothers had the second dose of their vaccine in infants who contracted or did not contract COVID-19 during the study period were 6.5 and 6.8 months, respectively (Table 1). These findings explain why the rate of COVID-19 in the breastfed only/dominant until the age of six months group was comparable to that of the other group throughout the study period.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAlthough we found a protective effect against COVID-19 with the adjusted HR of 1.63 (P = 0.09) in the breastfed only/dominant group until the age 12 months, and whose mothers had completed two doses of vaccine before the infants were 6 months of age with an adjusted HR of 3.77 (P = 0.05), the protective effect was not statistically significant. \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAntibodies to SARS-CoV2 have been identified in the breast milk of mRNA-vaccinated mothers \u003csup\u003e11,14,15\u003c/sup\u003e, but to the best of our knowledge, no study to date has examined the benefit of a non-mRNA vaccine-recipient mother in the mother’s breast milk in preventing infants from contracting COVID-19. Our findings suggest that mothers receiving non-mRNA vaccines might be as beneficial in preventing infants from contracting COVID-19 as mRNA vaccines, since the majority of mothers with a completed COVID-19 vaccination regimen prior to their infants reaching the age of 6 months had received non-mRNA vaccines.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe study had several limitations: firstly, there was a limited number of infants whose mothers had received complete COVID-19 vaccination regimens before the infants reached 6 months of age; secondly, there was a very limited number of mothers who had received an mRNA vaccine before their infants reached the age of 6 months, making it impossible to compare the efficacy between these two vaccine groups; and finally, none of the infants were exclusively fed formula milk so the infants might have gotten some passive antibodies from their breast milk.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWe found that the breast milk of mothers who have received the COVID-19 vaccination may help shield their infants from the virus, and that mothers who have had COVID-19 can nurse without raising the risk of SARS-CoV-2 transmission to the infants. Nevertheless, the results were not statistically significant due to the limited number of sample sizes. To draw a conclusion regarding these findings, additional research is required.\u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eRole of the Funder/Sponsor:\u003c/strong\u003e The funding organization had no role in the design or conducting of the study; the collection, management, analysis, and interpretation of the data; the preparation, review, or approval of the manuscript; or the decision to submit the manuscript for publication.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors wish to thank Kemmapon Chumchuen for assistance with data analysis, and David Patterson, an English teacher and writing consultant, for help with the English, both of whom work with the Faculty of Medicine, Prince of Songkla University.\u003c/p\u003e\n\u003cp\u003eWe received permission from Merck Sharp \u0026amp; Dohme LLC to collect data from the participants of the V114-032/PNEU-ERA research study at Site 0005 (NCT04193215). \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eK.L. wrote the main manuscript text; N.T, P.K, S.K, P.R, and V .K gathered information and performed data entry. All authors reviewed the manuscript.\u0026quot;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eWHO. COVID-19. [accessed 2023 Apr 1]. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://covid19.who.int/\u003c/span\u003e\u003cspan address=\"https://covid19.who.int/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWorldometer. COVID-19 coronavirus pandemic. 2019. [accessed 2023 Apr 1]. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.worldometers.info/coronavirus/\u003c/span\u003e\u003cspan address=\"https://www.worldometers.info/coronavirus/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGross R, Conzelmann C, Muller JA, et al. Detection of SARS-CoV-2 in human breastmilk. Lancet. 2020;395:1757\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMurano Y, Yamahira S, Shoji H, et al. Evaluation of the transmission of SARS-CoV-2 through breast milk: a case series. Front Pediatr. 2023;11:1160790.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePeng S, Zhu H, Yang L, et al. A study of breastfeeding practices, SARS-CoV-2 and its antibodies in the breast milk of mothers confirmed with COVID-19. Lancet Reg Health West Pac. 2020;4:100045.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBauerl C, Randazzo W, Sanchez G, et al. SARS-CoV-2 RNA and antibody detection in breast milk from a prospective multicentre study in Spain. Arch Dis Child Fetal Neonatal Ed. 2022;107:216\u0026ndash;21.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEsteve-Palau E, Gonzalez-Cuevas A, Guerrero ME, et al. Quantification and progress over time of specific antibodies against severe acute respiratory syndrome coronavirus 2 in breast milk of lactating women vaccinated with BNT162b2 Pfizer-BioNTech Coronavirus Disease 2019 Vaccine (LacCOVID). Open Forum Infect Dis. 2022;9:ofac239.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDuncombe CJ, McCulloch DJ, Shuey KD, et al. Dynamics of breast milk antibody titer in the six months following SARS-CoV-2 infection. J Clin Virol. 2021;142:104916.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBauerl C, Zulaica J, Rusu L, et al. Assessment of SARS-CoV-2 neutralizing antibody titers in breastmilk from convalescent and vaccinated mothers. iScience. 2023;26:106802.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJuncker HG, Mulleners SJ, van Gils MJ et al. Comparison of SARS-CoV-2-specific Antibodies in Human Milk after mRNA-Based COVID-19 Vaccination and Infection. Vaccines (Basel) 2021; 9(12).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEsteve-Palau E, Gonzalez-Cuevas A, Guerrero ME, et al. Quantification of specific antibodies against SARS-CoV-2 in breast milk of lactating women vaccinated with an mRNA vaccine. JAMA Netw Open. 2021;4:e2120575.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWittawatmongkol O, Bunjoungmanee P, Kosalaraksa P, et al. Immunogenicity and reactogenicity of fractional, heterologous primary COVID-19 vaccination schedules with BNT162b2 boosters in 5-11-year-old Thai children: A multicenter, prospective, double-blind, randomized control trial. Vaccine. 2023;41:5834\u0026ndash;40.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNiyomnaitham S, Toh ZQ, Wongprompitak P, et al. Immunogenicity and reactogenicity against the SARS-CoV-2 variants following heterologous primary series involving CoronaVac and ChAdOx1 and BNT162b2 plus heterologous BNT162b2 booster vaccination: An open-label randomized study in healthy Thai adults. Hum Vaccin Immunother. 2022;18:2091865.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNarayanaswamy V, Pentecost BT, Schoen CN, et al. Neutralizing Antibodies and Cytokines in Breast Milk After Coronavirus Disease 2019 (COVID-19) mRNA Vaccination. Obstet Gynecol. 2022;139:181\u0026ndash;91.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCalvo-Lerma J, Bueno-Llamoga P, Bauerl C, et al. Persistence of Anti SARS-CoV-2 antibodies in breast milk from infected and vaccinated women after in vitro-simulated gastrointestinal digestion. Nutrients. 2022;14:2117.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 to 2 are available in the Supplementary Files section\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"SARS-CoV-2, COVID-19, breastfeeding, vaccine, infants","lastPublishedDoi":"10.21203/rs.3.rs-4780196/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4780196/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eObjective: \u003c/strong\u003eTo compare the COVID-19 transmission rates between infants who were primarily breastfed and those formula fed in mothers who received at least 2 doses of the COVID-19 vaccines.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e A prospective longitudinal study was conducted during the Omicron wave (January 1-October 1, 2022). Infants who exhibited respiratory symptoms were tested for SARS-CoV-2 by RT-PCR.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults: \u003c/strong\u003eOf 234 infants, 66 (28.2%) tested positive for SARS-CoV-2, with 63 out of the 66 (95.5%) having a mother with COVID-19, and a median (IQR) age at diagnosis of 11.3 (10.8-11.9) months. The proportions of COVID-19 in 6- and 12-month breastfed and formula fed dominant infants were 27.0% vs. 31.0%, p =0.53 and 21.1% vs. 31.3%, p =0.11, respectively.\u003c/p\u003e\n\u003cp\u003eIn the multivariate Cox regression models, both 6- and 12-month breastfed only/dominant infants had a protected effect against COVID-19 with hazard ratios (HRs, 95% CI) of 1.50 (0.90, 2.51), p =0.13 and 1.63 (0.90, 2.51), p =0.09, respectively. Maternal vaccine regimens had no protective effect against COVID-19 with the HR of 0.86 (0.49, 1.52), p =0.61. In sub-group analysis, infants with a mother that had received 2 doses within 6 months and were breastfed only/dominant at 12 months had a protected effect against COVID-19 with the HR of 3.77 (0.77, 18.43), p =0.05.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e: Mothers who have experienced COVID-19 can nurse without increasing the risk of SARS-CoV-2 transmission. Despite the possibility that breastfeeding mothers who receive the COVID-19 vaccine can shield their infants from the virus, the statistical evidence is insignificant.\u003c/p\u003e","manuscriptTitle":"Effectiveness of COVID-19 vaccination in breastfeeding women in preventing SARS-CoV-2 infection in infants","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-26 20:49:45","doi":"10.21203/rs.3.rs-4780196/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"03e5ba16-7323-4915-99f9-493dd19a5f11","owner":[],"postedDate":"August 26th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-04-03T21:38:13+00:00","versionOfRecord":[],"versionCreatedAt":"2024-08-26 20:49:45","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4780196","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4780196","identity":"rs-4780196","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}