Fertility outcomes in women undergoing Assisted Reproductive Treatments after COVID-19 vaccination: A prospective cohort study.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a virus that wreaked havoc in the lives of millions of people across the world since its appearance in December 2019. The disease it causes is named Coronavirus disease-19 (COVID-19). The toll it has taken on the lives and livelihoods of people in a short timespan is unparalleled by any other microbiological agent in one entire century ( 1 ). There is no known effective cure for the disease caused by SARS-CoV-2 infection. However, preventive methods have been widely used effectively ( 2 , 3 ). Apart from non-pharmacological measures like masking, social distancing and handwashing one effective way to prevent disease severity caused by SARS-CoV2 is vaccination. Vaccination has been proven to reduce disease severity and deaths caused by the virus ( 4 ). There were some concerns regarding vaccines amongst prospective parents that led to initial vaccine hesitancy ( 5 ). One of them was that vaccines may lower fertility. One possible reason cited for this concern was that a common adverse-effect following vaccination is fever and that fever in early pregnancy could affect pregnancy continuation or healthy fetal development. Indeed, phase 1/2 trials and real world studies on different vaccines have found fever as an adverse effect reported by 25-40% of recipients after first or second dose vaccine ( 6 ). Also, a meta-analysis of observational studies, found an association between fever in early pregnancy and fetal neural tube defects [pooled odds ratio (OR)=2.90, 95% confidence interval (CI)=2.22-3.79] ( 7 ). In this analysis, the authors found that the risk for fetal adverse congenital anomalies including neural tube defects, congenital heart defects and oral clefts was linked to the degree of fever with temperatures ≥38.9°C for ≥24 hours increasing and antipyretic ingestion reducing that risk respectively, suggesting that hyperthermia alone may pose an independent risk apart from the pathogenicity of the offending agent to the development of congenital anomalies. However, early studies in mice have not revealed any detrimental effect of Chimpanzee Adenoviral vector vaccine against SARS-CoV2 developed by Oxford group (ChAdOx1 nCoV-19) on reproduction or fetal pup toxicity ( 8 ). Also, an interim report published by the CDC based on its v-safe registry of pregnant women who have received COVID-19 messenger Ribonucleic Acid vaccines (COVID-19 mRNA vaccine) and reports from 913 vaccinated pregnant women in Israel, found no evidence of an increase in adverse events amongst women with completed pregnancies or their offspring ( 9 , 10 ). The question of whether COVID-19 vaccination could affect fertility, and not fetal outcomes, however, had not been addressed through any published study till November 2021, although societies had issued guidelines before this that fertility concerns are unfounded in the absence of a plausible explanation ( 11 , 12 ). In the correspondence addressed to the Lancet editor, the authors of the Oxford Vaccine Development group, sub analysed their data to look at fertility rates in women who participated in the phase 3 ChAdOx1 vaccine trial ( 13 ). They found that spontaneous fertility rate, as measured by spontaneous conceptions in the trial period, were similar in the controls (n=43) and the test vaccinated group (n=50) with a fertility rate ratio of 1·14 (0.76-1.71). Real world natural fertility assessment amongst couples having unprotected regular intercourse might require an epidemiological study, hence might be expensive and time-consuming. Fertility could also be assessed as a measure of success after assisted reproduction. In vitro fertilization (IVF), a form of assisted reproductive technique, is undertaken routinely at several centres in couples for various indications like severe male factor infertility, tubal infertility, severe endometriosis or unexplained infertility. Of all vaccine types, BNT162b2 (mRNA vaccine developed by Pfizer) is the most researched in IVF populations. In a cohort of 35 consecutive consenting women undergoing IVF, Bentov et al. ( 14 ), identified COVID 19 IgG antibody from follicular fluid in those who received mRNA vaccine and in those who were recovering from COVID 19. But they did not find significant differences in the outcomes of human chorionic gonadotropin (hCG) day estrogen and progesterone, follicular fluid progesterone, oocyte numbers or oocyte maturity rates in the three study arms of those vaccinated (n=9), those recently recovering from COVID 19 infection (n=9) and those unvaccinated and uninfected (n=14). Similarity in IVF stimulation parameters and embryological results were also seen by Orvieto et al. ( 15 ) when comparing outcomes in 36 individuals in their pre and post BNT162b2 vaccinated states. Recent publications involving 1583 women by Wu et al. ( 16 ) exist but are limited by their retrospective nature and the type of vaccine studied, i.e. inactivated COVID-19 vaccination alone. The study question of whether recent COVD-19 vaccination could alter fertility outcomes can therefore be addressed in women undergoing IVF through a prospective cohort study involving adequate number of individuals, accounting for appropriate vaccine types and confounders and studying patient-oriented outcomes. This was our study objective.

A total of 734 oocyte retrieval cycles took place in the study duration at the centre of study, of which 617 met the inclusion criteria. Of these 63 declined to participate and 52 cycles had incomplete information on vaccine data, leaving a total of 502 OCR cycles, having complete information available for analysis ( Fig .1 ). Because of repeated COVID waves (January-February 2022) since study initiation, screening criteria application and refusal of some patients to participate, the expected sample size of 712 could not be met. Participant flowchart showing vaccine status at OCR: VS(OCR) and at embryo transfer: VS(tr). OCR; Oocyte retrieval, VS(OCR); Vaccine status at OCR, and VS(tr)=; Vaccine status at embryo transfer A total of 179 cumulative ongoing pregnancies resulted from 502 oocyte retrieval cycles (35.7%), through a total of 582 intended embryo transfer cycles (30.7%) in the study duration. Of these 135 ongoing pregnancies resulted from 472 first transfers (28.6%), 39 from 97 second transfers (39.8%), 4 from 11 third transfers (36.4%) and 1 from 1 fourth transfer (100%). Vaccine status (VSOCR) for 502 oocyte retrieval cycles was no dose=63, 1 dose=87 and ≥2 dose=352. Of those vaccinated, 71.8% had received ChAdOx1, an adenoviral vector vaccine manufactured by Astra Zeneca, 20.3% had received Covaxin, (inactivated whole virion vaccine, manufactured by Bharat Biotech, India) and 7.9% had received other mRNA vaccines like Pfizer/Moderna. Vaccine status (VSTr) for 582 transfer cycles was: no dose=66, 1 dose=82 and ≥2 doses=434 ( Table S1 , See Supplementary Online Information at www.ijfs.ir ). Median time to embryo transfer from last vaccine dose was 146 days (IQR: 80-220). None of these women were lost to follow up. The distribution of demographic data and cycle characteristics based on VSOCR are shown in Table 1 . It reveals significant baseline differences in women’s age, with those receiving no doses being younger than those receiving 1 or ≥2 dose (31.9 ± 4.6 vs. 33 ± 3.3 vs. 34.3 ± 3.9, P<0.01). This reflected on hCG day mean estradiol levels (2251 vs. 1830 vs. 1609, P<0.01) and marginally though insignificantly on total oocyte numbers: 13.1 ± 8.4 vs. 11.4 ± 7.7 vs. 10.9 ± 6.4, P=0.09 (ß=0.27, 95% CI=-0.65 to 0.89). The mean total utilizable embryos: 2.7 ± 1.8 vs. 2.5 ± 1.9 vs. 2.7 ± 2.0, P=0.78 (ß=0.42, 95% CI=0.15 to 0.69), and mean oocyte utilization rate: 21.2 ± 13.2 vs. 25.1 ± 19.0 vs. 26.7 ± 18.8, P=0.08, (ß=3.94, 95% CI=1.26 to 6.23); in the three cohorts appeared to increase with increasing vaccine doses. ( Table 2 ). Beta reflects the unit change in oocyte numbers, total utilizable numbers and total utilization rates with each dose increase in vaccine which although appears to be a change in a positive direction, but the value appears too small for it to make a clinical difference. Embryological outcomes based on type Specific Vaccine Status also did not reveal any significant differences in mean total oocytes, mean total utilizable embryos or mean oocyte utilization rate ( Table S2 , See Supplementary Online Information at www.ijfs.ir ). Ongoing pregnancy rates per embryo transfer cycle are shown in Table 3. No significant differences emerged in the ongoing pregnancy rates (27.3% vs. 24.4% vs. 32.5%, aOR=1.38, 95% CI=0.3-5.6, P=0.52) or pregnancy loss rates per embryo transfer cycle (13.6% vs. 13.4% vs. 15.2%, aOR=0.97, 95% CI=0.18-5.2, P=0.97) between the three cohorts. Cumulative ongoing pregnancy rates per oocyte retrieval cycle till at least six months from oocyte retrieval, were also not different based on vaccination status. (36.5% vs. 34.5% vs. 35.5%, aOR=1.53, 95% CI=0.57-4.07, P=0.35). Within the Cohort of ≥1 dose, vaccine type did not influence clinical outcomes of ongoing clinical pregnancies per embryo transfer cycle or cumulative pregnancies per oocyte retrieval cycle ( Table S3 , See Supplementary Online Information at www.ijfs.ir ). To assess the role of time since last vaccine dose on embryo transfer outcomes, a ROC was established using time since last vaccine dose till embryo transfer as the independent variable and ongoing pregnancies as the dependent variable. The ROC revealed a sharp demarcation at 190 days, roughly corresponding to 6 months, being non-discriminatory for outcomes above this interval and rising above the line of no significance for intervals under this. This suggested that any vaccination effect on embryo transfer outcomes existed till up to 6 months ( Fig .2 ). ROC analysis using time since last dose and outcomes of embryo transfer. A. ROC curve for all time intervals from vaccination to embryo transfer showing a sharp demarcation at the intersection with the marked line. This point represents 190 days suggesting that any vaccination effect on embryo transfer outcomes ceases to exist beyond 190 days. B. ROC curve showing association between ongoing pregnancies per embryo transfer with COVID-19 vaccination for intervals <190 days [AUC=0.59 (95% CI=0.54-0.66, P<0.01]. ROC; Receiver operator curve, AUC; Area under curve, and CI; Confidence interval. Demographic detail and cycle characteristics as per vaccine status at oocyte retrieval (n=502) Data are presented as mean ± SD or n (%). Significance level or P value calculated by using a; Chi square test for categorical variables, b; One way ANOVA for normally distributed con- tinuous variables, c; Kruskal Wallis test for non-normally-distributed continuous variables, BMI; Body mass index, AMH; Anti-mullerian hormone, OCR; Oocyte retrieval, COS; Controlled ovarian stimulation, Gn; Gonadotropin, hMG; Human menopausal gonadotropin, rec; Recombinant, FSH; Follicle stimulating hormone, LH; Luteinizing hormone, hCG; Human chorionic gonadotropin, GnRH; Gonadotropin releasing hormone agonist, IVF; In vitro fertilization, and ICSI; Intracytoplasmic sperm injection. Embryological outcomes and cumulative ongoing pregnancy outcomes as per vaccine status at oocyte retrieval (n=502) Data are presented as mean ± SD or n (%). *; P value is unadjusted and calculated using chi square test for categorical variables and one way ANOVA for continuous variables, a; Oocyte retrieval cycles resulting in intrauterine viable pregnancy having cardiac activity at or beyond 12 weeks as a result of transfer of one or all embryos formed. Oocyte retrieval cycles that did not result in an ongoing pregnancy till the study termination date were labelled as 0 and those that did were labelled as 1. The label 0 includes cycles with no utilizable embryos, cycles with no pregnancy after transfer of all utilizable embryos, cycles with a miscarriage prior to 12 weeks and cycles with embryos continuing to be in storage till study termination, b; Regression coefficient calculated for continuous outcomes using Linear regression and, c; Odds ratio calculated for binary outcomes using logistic regression. Adjustments have been made for pre-treatment variables of age, infertility duration, infertility diagnosis, previous pregnancies, BMI, consultant administering treatment, AMH, prior covid infections, vaccine doses and vaccine type, CI; Confidence interval, BMI; Body mass index, and AMH; Anti-mullerian hormone. Clinical outcomes as per vaccine status at ET (n=582) Data are presented as n (%). *; Adjusted odds ratio calculated using Binary Logistic regression after adjusting for age, infertility duration, previous pregnancies, infertility diagnosis, consultant delivering treatment, BMI, AMH, prior COVID infections, whether fresh or frozen embryo transfer, vaccine type and number of vaccine doses in 582 embryo transfer cycles. CI; Confidence interval, NA; Not applicable, and ET; Embryo transfe For intervals <190 days, AUC was significant (0.59, 95% CI=0.54-0.66, P<0.01) suggesting that as time since vaccine increased from 0-190 days, the ongoing pregnancy results marginally increased ( Table S4 , See Supplementary Online Information at www.ijfs.ir ). The effect was most pronounced for intervals up to 60 days from the last dose of vaccine, with a sensitivity, specificity, positive predictive value, and negative predictive value for ongoing pregnancy of 89.4, 21, 33.7 and 80.9% respectively. The adjusted OR for ongoing pregnancy above 60 days was 2.85 (95% CI=1.50-5.46, P=0.001, Table 4 ). Effect of demographic and vaccine associated variables on odds of ongoing pregnancy in vaccine exposed embryo transfer cycles (n=516) *; Logistic regression analysis has been used to calculate adjusted odds of ongoing pregnancy in embryo transfer cycles that had prior vaccine exposure and CI; Confidence interval.

This prospective observational cohort study involving 502 IVF cycles, does not find an overall influence of COVID 19 vaccination on IVF outcomes of mean total utilizable embryos and mean oocyte utilization rates, or ongoing pregnancies and pregnancy losses per embryo transfer cycle or cumulative ongoing pregnancies per oocyte retrieval cycle based on COVID-19 vaccination status. However, in the vaccinated cohort, it does show a marginal influence of time elapsed between last vaccine dose to embryo transfer, with durations shorter than 60 days tending to lower ongoing pregnancies. Our study results show that the vaccinated arm and the unvaccinated cohorts might have a slight difference in AMH values with the vaccinated arm having lower mean AMH values than the unvaccinated. We do not believe that vaccination affected or lowered their ovarian reserve since, existing studies have unequivocally shown that COVID-19 vaccination does not influence ovarian reserve as seen through AMH testing three months to one year after vaccination ( 18 , 19 ). In our study, the difference in AMH between cohorts is accounted for by a difference in women’s mean age. As to why the vaccinated arm was marginally older than the unvaccinated arm could be explained either as a chance finding or perhaps that the younger women either did not have early access to vaccines due to limited initial vaccine availability ( 20 ) or that they did not feel the need to get vaccinated early on because of the perception of milder COVID disease in the younger population. Our study results also demonstrate that despite being older and having lower ovarian reserve, parameters that significantly influence cumulative ongoing pregnancies in IVF, both the vaccinated cohorts continued to have similar ongoing pregnancy rates as the unvaccinated cohort. This finding although contradictory to conventional wisdom, can be explained by the fact that vaccinated individuals can be considered to have greater protection from SARS CoV-2 viral transmission and manifestation of severe disease. Unvaccinated individuals, unless previously exposed to the virus, do not have that protection and hence likely to contract the virus leading to cytokine release, activation of cellular and humoral immunity, and development of fever, factors that negatively influence embryo implantation and miscarriages ( 21 ). Based on this premise, the expectation is that, during the pandemic with ongoing susceptibility to new infections, unvaccinated individuals should either have a similar or lower implantation rate than the vaccinated individuals. But the opposing effect of younger age and higher AMH in the unvaccinated cohort, perhaps neutralizes that effect in our study. Our results that embryological and clinical outcomes are not affected by COVID-19 vaccination are similar to the study by Wu et al. ( 16 ) but different from those reported by Chen et al. ( 22 ). Wu et al. ( 16 ), in a retrospective study, compared IVF outcomes in 240 women vaccinated with either Corona- Vac or Sinopharm before ovarian stimulation with 1343 unvaccinated women. Linear regression analysis revealed that the number of oocytes retrieved (regression coefficient (B)=-0.299, P=0.264), embryos suitable for transfer (B=-0.203, P=0.127) and blastocysts (B=-0.250, P=0.105) were not associated with the status of vaccination before ovarian stimulation, after adjusting for confounders. The ongoing pregnancy rate in women of the vaccinated group was also not significantly lower than that in the unvaccinated group (36.3 vs. 40.7%, P=0.199) (adjusted OR=0.91, 95% CI=0.68-1.22, P=0.52) ( 16 ). Whereas, in another retrospective observational study, Chen et al. ( 22 ) compared IVF outcomes in 268 women receiving inactivated or recombinant COVID-19 vaccination with 268 controls, and observed a decreased fertilization (63.07 vs. 67.13%, P=0.01) and mature oocyte number (8.86 ± 6.13 vs. 9.28 ± 5.38, P=0.01) in women vaccinated with the inactivated vaccine when compared to unvaccinated women. However, Chen et al’s study reaffirmed the safety of COVID-19 vaccination, with respect to blastulation, implantation, clinical pregnancy, and miscarriage rates irrespective of the type of vaccine received. The other significant finding of our study was that within the vaccinated cohort, time since last dose influenced embryo transfer results marginally with an AUC of 0.59. The best ongoing pregnancy rates were seen 60 days after the last vaccine dose was received. This time influence appears contrary to the above-mentioned results which do not indicate influence of vaccination on embryo transfers, perhaps because in our study only 14.9%, n=87 of all transfers were at intervals shorter than sixty days and only in this interval, the influence of vaccine on embryo transfer outcomes appeared negative. Influence of time elapsed since last dose on embryo transfer outcomes has been seen by other authors too. A large cohort study from China by Shi et al. ( 23 ) looked at the effect of time since inactivated SARS CoV 2 vaccine on embryo transfer outcomes and recommended that it was best to wait for two months after the last vaccine dose before performing embryo transfers. Previous studies have revealed that the type I viral envelope protein and human syncytin-1 protein involved in the formation of the placenta share analogous structural features ( 24 ). It has been claimed that vaccine induced antibodies against the spike protein may cross-react with syncytin-1 leading to poor implantation and early pregnancy losses. COVID-19 vaccine (ChAdOx1) mediated antibody generation peaks in the body at two weeks and thereafter starts to decline with a mean halflife of 79 days ( 25 ). It is therefore possible to see the weak time effect on embryo transfer outcomes in our study as the effect of activation of peak vaccine mediated immunity on endometrial receptivity or implantation in the initial days. Contrarily, one other large scale retrospective study by Brandão et al. ( 26 ), comparing 890 individuals receiving mRNA vaccine with 3272 unvaccinated historical controls from before the pandemic, and Chen et al’s ( 22 ) retrospective study involving 280 women that received inactivated vaccine do not find the influence of time elapsed since vaccination on embryo transfer outcomes. Therefore, it is also possible that other unaccounted for factors are at play in our study, like new COVID infections after embryo transfer, a variable that our study does not account for, and that this could have confounded the time effect. However, the outcome of mean oocyte utilization accounts for all episodes of prior and current infections as well as vaccine status and the finding that the embryological outcomes of mean total utilizable embryos and mean oocyte utilization rate are unimpacted by vaccine status, vaccine type, time since vaccine dose or previous COVID infections is reassuring to clinicians and patients alike. To the best of our knowledge, three studies on fertility after ChAdOx1 exist in the literature so far, one from the phase three trial setting of ChAdOx1 vaccine ( 13 ), one in mice to demonstrate no known fetal toxicity ( 8 ) and one in men, demonstrating no difference in semen parameters before and after ChAdOx1 vaccination ( 27 ). And none of these looks at the time influence of ChAdOx1 on embryo transfer outcomes. The strengths of our study therefore are, analysis of the effect of type specific vaccine effects on IVF outcomes, chiefly the less studied Adenoviral Vector Vaccine, ChAdOx-1, and a regression analysis accounting for the effect of confounders like vaccine type, vaccine doses and previous COVID infections on primary outcomes. The limitations include failure to meet an appropriate sample size.

COVID-19 vaccination does not appear to influence embryological outcomes like fertilization rates, mean total utilizable embryos or mean oocyte utilization rate or cumulative ongoing pregnancies per oocyte retrieval cycle. Duration since vaccination has a marginally significant negative effect on embryo transfer outcomes, with intervals less than 60 days since vaccination likely to negatively affect results. Future research should secondarily examine the results from existing literature, taking into account specific vaccine types to ascertain these findings.

Institutional Ethics Committee Approval (Ethics Committee, Sir Ganga Ram Hospital) was received for this prospective cohort study vide letter No. EC/08/21/1948. Informed Consent was taken from all participants. The eligibility criteria included couples undergoing IVF or intracytoplasmic sperm injection (ICSI) cycles at the centre of study. Inclusions were couples undergoing IVF/ICSI with self-eggs and transfer in self. Exclusions were donor oocyte cycles, donor sperm cycles, surrogacy cycles, women undergoing IVF for fertility preservation and those refusing to participate. The study included women undergoing oocyte retrieval cycles from 1st June 2021 to 31st March 2022. Results from all embryo transfers occurring till 1st October 2022 (i-e.) six months after the last oocyte retrieval cycle, were analysed. Demographic data including age (in years), infertility duration (in years), body mass index (Kg/m 2 ), infertility indication (male, tubal, unexplained, endometriosis, combined), previous pregnancies (no prior pregnancies, previous pregnancies resulting in no live birth, previous pregnancies resulting in at least one live birth), Anti-Mullerian Hormone (ng/ml), history of previous COVID-19 infection (yes/no) and IVF cycle data including gonadotropin type [human menopausal gonadotropin (hMG), recombinant follicle stimulating hormone (FSH) or combined], total gonadotropin dose (IU), estradiol on the day of ovulation trigger (pg/ml) and type of ovulation trigger (hCG/GnRH agonist/dual) were collected. Data on retrieved oocyte number (n), fertilization rates in IVF and ICSI cycles (%), total utilizable embryos formed (n) and oocyte utilization rates (%) were calculated. Total utilizable embryos were calculated as the sum of all day-3 embryos and day 5/6 blastocysts formed from one cycle that were either transferred or cryopreserved. Mean oocyte utilization rate was calculated as the percentage of total utilizable embryos to total retrieved oocytes. Data on cycles with no embryos available for transfer, cycles with embryos continuing to be in cryo-storage till study termination date and results of each embryo transfer cycle, whether resulting in no pregnancy, pregnancy loss or an ongoing pregnancy were recorded. Positive pregnancy was defined as serum bhCG value of >25 mIU/ml 11 days after a blastocyst transfer or 13 days after a day-3 embryo transfer. An ongoing pregnancy was defined as the presence of gestational sac in utero with cardiac activity seen on an ultrasound scan at twelve weeks gestation. A pregnancy loss was defined as all pregnancies from the point of positive bhCG that resulted in a pregnancy loss till 12 weeks gestation including a biochemical pregnancy loss, blighted ovum, missed abortion and an ectopic pregnancy. Dates of oocyte retrieval, fresh and frozen embryo transfer were recorded as well. Vaccine data including type of vaccine received: whether inactivated whole virion vaccine, adenoviral vector vaccine or mRNA vaccine; number of doses received, and their dates of receipt were collected on the day of oocyte retrieval as per their details on the COWIN app. Patient reported adverse events, if any, after vaccination were recorded. Since vaccine status is a time dependent variable and embryo transfer could take place remote from oocyte retrieval date, vaccine status was checked once more on the day of embryo transfer and vaccine status reassigned at transfer day. Three comparison cohorts were created at two time points based on vaccination status (VS) as those with no prior COVID-19 vaccination exposure and those with 1 and ≥2 dose COVID-19 vaccination exposure. The first timepoint was at oocyte retrieval (VSOCR) and the second was at embryo transfer (VSTr). Embryological outcomes were compared in the three VSOCR cohorts. And embryo transfer outcomes were compared in the three VSTr groups. Similarly, time since last vaccine dose was calculated twice as t(OCR) as the difference in days between last dose to oocyte retrieval and t(Tr) as the difference in days between last dose to embryo transfer. Embryological outcomes studied were mean total oocytes retrieved, fertilization rates, total utilizable embryos and mean oocyte utilization rates per oocyte retrieval cycle. Embryo transfer outcomes studied were ongoing pregnancy rates and pregnancy loss rates per fresh or frozen embryo transfer cycle. Cumulative ongoing pregnancy rates per oocyte retrieval cycle were also calculated and defined as ongoing pregnancies resulting from transfer of all fresh and frozen embryos formed in one oocyte retrieval cycle. The oocyte retrieval cycle was considered completed if it resulted in an ongoing singleton/twin pregnancy or in the absence of an ongoing pregnancy when all utilizable embryos were exhausted or the study duration of six months from oocyte retrieval was over. Based on our previously published work that demonstrates ( 17 ) a 40% ongoing pregnancy rate per started cycle ( 16 ), and assuming a 10% lowering of ongoing pregnancies in the vaccinated arm, and an 80% power with a 5% error margin, a total of 712 subjects were required to estimate a significant difference in ongoing pregnancy rate. Comparative analysis was done amongst the three cohorts using One way ANOVA for normally distributed numerical data and Kruskal Wallis test for skewed data. Categorical variables were compared using the chi-square test. Regression coefficient beta (ß) was calculated using linear regression analysis for mean total utilizable embryos and mean oocyte utilization rates. Adjusted odds ratios (OR) were calculated using logistic regression analysis for ongoing pregnancy rates, pregnancy loss rates and cumulative pregnancy rates. Appropriate adjustments for confounders of age, infertility duration, infertility diagnosis, consultant administering treatment, anti-mullerian hormone (AMH), prior covid infections, Vaccine doses and vaccine type were made to calculate ß and aOR. ß indicates the value by which the mean of dependent numerical variables i.e. total utilizable embryos and mean oocyte utilization rates would increase, or decrease for every unit increase in the independent variable which in this case was the number of vaccine doses, after adjusting for the above stated confounders. Similarly, aOR indicates the OR for dependent binary variables: ongoing pregnancy rate, pregnancy loss rate and cumulative ongoing pregnancy rate in the three vaccine cohorts after adjusting for above stated confounders. To determine the influence of time elapsed since vaccine administration to embryo transfer on ongoing pregnancy rate, a receiver operator curve (ROC) was drawn and area under the curve (AUC) estimated. If time influenced results significantly, then a cut-off for the time interval that most discriminated between positive and negative results was determined based on maximum sensitivity and specificity values. aOR for ongoing pregnancy rate per embryo transfer in the vaccinated cohort as per the time interval cut-off was additionally calculated using binary logistic regression. All analyses were done on Statistical Product and Service Solutions software (version 28).