COVID-19 Vaccination and Infertility Treatment Outcomes

Impact of mRNA and Inactivated COVID-19 Vaccines on Ovarian Reserve

Objectives: This study aimed to elucidate the effects of messenger RNA (mRNA) and inactivated coronavirus disease 2019 (COVID-19) vaccines on ovarian histology and reserve in rats. Methods: Thirty female Wistar albino rats, aged 16-24 weeks, were randomly divided into three groups (n = 10): control, mRNA vaccine, and inactivated vaccine groups. Each vaccine group received two doses (on day 0 and day 28) at human-equivalent doses. Four weeks post-second vaccination, ovarian tissues were harvested for analysis. Results: Immunohistochemical analysis was performed to evaluate the expression of transforming growth factor beta-1 (TGF-β1), vascular endothelial growth factor (VEGF), caspase-3, and anti-Müllerian hormone (AMH) in ovarian follicles. Both vaccines induced significant increases in TGF-β1, VEGF, and caspase-3 expression, with more pronounced effects in the mRNA vaccine group. Conversely, AMH expression in the granulosa cells of primary, secondary, and antral follicles showed marked reductions (p < 0.001). The counts of primordial, primary, and secondary follicles decreased significantly in the inactivated vaccine group relative to controls and further in the mRNA vaccine group compared to the inactivated group (p < 0.001). Additionally, the mRNA vaccine group exhibited a decrease in antral and preovulatory follicles and an increase in atretic follicles compared to the other groups (p < 0.05). The serum AMH level was diminished with the mRNA vaccination in comparison with the control and inactivated groups. Conclusions: Our findings suggest that both mRNA and inactivated COVID-19 vaccines may detrimentally impact ovarian reserve in rats, primarily through accelerated follicular loss and alterations in apoptotic pathways during folliculogenesis. Given these observations in a rat model, further investigations into the vaccines' effects on human ovarian reserve are needed.

The Safety and Efficacy of inactivated COVID-19 vaccination in couples undergoing assisted reproductive technology: A prospective cohort study

BACKGROUND

The safety of the COVID-19 inactivated vaccine on pregnancy outcomes in couples undergoing assisted reproductive technology remains uncertain due to limited and speculative evidence. Existing studies primarily focus on the vaccination status of females, with scant information available regarding the vaccination status of male partners. Moreover, there is minimal research tracking live birth outcomes.

OBJECTIVE(S)

The objective of this study was to evaluate the impact of COVID-19 inactivated vaccine administration on the outcomes of in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) cycles in infertile couples in China.

METHODS

This prospective cohort study involved couples undergoing IVF treatment at Sichuan Jinxin Xinan Women & Children's Hospital from August 2021 to September 2022. Based on whether they received vaccination before ovarian stimulation, the couples were divided into the vaccination group and the non-vaccination group. We compared the laboratory parameters and pregnancy outcomes between the two groups.

RESULTS

After performing propensity score matching (PSM), we observed similar live birth rates (41.23% vs. 44.08%, P = 0.555), clinical pregnancy rates (52.61% vs. 54.98%, P = 0.625), biochemical pregnancy (62.56% vs. 63.98%, P = 0.762), and ongoing pregnancy rates (49.76% vs. 51.18%, P = 0.770) between the vaccinated and unvaccinated women. Also, no significant disparities were found in terms of embryo development and laboratory parameters between the groups. Moreover, male vaccination had no impact on patients' pregnancy outcomes in assisted reproductive technology (ART) treatments (all P > 0.05). Additionally, there were no observable effects of vaccination on embryo development and pregnancy outcomes among couples undergoing ART (all P > 0.05).

CONCLUSION(S)

The findings suggest that COVID-19 vaccination did not have a significant effect on patients undergoing IVF/ICSI with fresh embryo transfer. Therefore, it is recommended that couples should receive COVID-19 vaccination as scheduled to help mitigate the COVID-19 pandemic.

Impact of COVID-19 Vaccination on Female Fertility

Despite evidence in previous literature regarding vaccine safety, more data were needed as concerns about COVID-19 vaccines were raised, particularly regarding their effects on female fertility, exacerbated by the widespread dissemination of information without scientific evidence. This study aims to answer the question: does COVID-19 vaccination have any impact on female fertility at a population level. In this ecological study, vaccination rates against COVID-19 and birth rates in 100 different countries were correlated. In addition, the correlation between these two rates of interest and the Gini index were also analyzed. Data were retrieved from the World Population Prospects document produced by the Population Division of the United Nations Department of Economic and Social Affairs, from the World Health Organization (WHO) website, and from the World Bank website. Statistical analyses were conducted using the ANOVA test, and Pearson's correlation using the JASP software. For all analyses, results were considered significant if P < 0.05. In evaluating the trend of the birth rate in the countries included in the study, a persistent reduction of approximately 1.66% per year was observed between 2010 and 2022. From 2019 to 2022, the decline was close to 5%, resulting in an annual average reduction of 1.68%, which is similar to previous years. Among the selected countries, until December 2021, the average number of vaccine doses administered was 137 per 100 inhabitants. There was no observed correlation between the number of vaccine doses administered in different countries and the variation in the birth rate per thousand inhabitants between 2019 and 2022 (Pearson's r = 0.075; P = 0.455). A correlation was found between the Gini index and the birth rate, considering the base year of 2022, with a Pearson's r value of 0.376 (P < 0.01). This correlation remained consistent for all other years. A negative correlation was found between vaccine doses and the Gini index, with a Pearson's r value of -0.219 (P = 0.040). The findings of this article, as well as previous scientific evidence, do not identify any correlation between COVID-19 vaccines and female fertility issues. The associations analyzed in this study indicate the safety of vaccines for reproductive health and contribute to reducing vaccine hesitancy among the population of childbearing age.

Effect of SARS-CoV-2 vaccination on the outcomes of assisted reproductive technology: A review

It has been over 4 years since the coronavirus disease 2019 outbreak, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). As an effective response to coronavirus disease 2019, the SARS-CoV-2 vaccines have been widely used around the world. However, couples who are planning to conceive naturally or by assisted reproductive technology (ART) are concerned about the impact of SARS-CoV-2 vaccines on pregnancy and offspring safety. Furthermore, in the initial stage of the epidemic, opinions among physicians and healthcare providers on whether ART patients should be immunized are divided due to the lack of data regarding the impact of the SARS-CoV-2 vaccine on ART. This is not the first, nor will it be the last time humans confront pandemics. It is time to summarize the experience about the effect of the SARS-CoV-2 vaccine on the outcomes of ART, which can provide a reference for the future. This paper reviewed relevant research, and significant adverse effects of the SARS-CoV-2 vaccine on the outcome of ART have not been observed. Considering the increased risk of serious complications in pregnant women infected with SARS-CoV-2, timely vaccination may be a wiser choice.

The type of COVID-19 vaccination does not affect reproductive function and pregnancy outcomes in infertile couples

Introduction

Studies on the effect of vaccine type and two other vaccines other than inactivated vaccines approved in China on in vitro fertilization (IVF) pregnancy outcomes are rare. To complement and confirm the existing findings, this research aimed to investigate whether there are adverse effects of different vaccine types in females and males on reproductive function and clinical pregnancy.

Methods

This retrospective study enrolled 6,455 fresh embryo transfer cycles at the First Affiliated Hospital of Zhengzhou University between May 1, 2021, and October 31, 2022. The primary outcome is the clinical pregnancy rate (CPR). At the same time, the secondary results are the number of oocytes retrieved, two pronuclei (2PN) rate, blastocyst formation rate, high-quality blastocyst rate, and semen parameters (volume, density, sperm count, forward motility rate, total motility rate, immobility rate, and DNA fragment index (DFI) rate).

Results

In the comparison of ovarian stimulation indicators, no statistically significant differences (P > 0.05) were found in Gn days, endometrial thickness, 2PN rate, metaphase 2 (MII) rate, high-quality embryo rate, and blastocyst formation rate. No significant differences (P>0.05) were found in age, body mass index (BMI), education level, and semen parameters (volume, density, sperm count, forward motility rate, total motility rate, immobility rate, and DFI rate) in these four groups. The multivariate regression model showed that neither the types of vaccines nor the vaccination status of both infertile couples significantly affected clinical pregnancy.

Discussion

The type of vaccine does not appear to have an unfavorable effect on ovarian stimulation, embryo development, semen parameters, and clinical pregnancy.

The effect of COVID-19 vaccination during IVF stimulation on cycle outcomes- a retrospective cohort study

The effect of the mRNA-BNT162b2 vaccine administered prior to fertility treatments has been addressed in several studies, presenting reassuring results. Cycle outcomes of patients receiving the vaccine during the stimulation itself have not been previously described. This retrospective cohort study included patients who received mRNA-BNT162b2-vaccine during the stimulation of fresh IVF cycles, between January-September 2021, age matched to pre-stimulation vaccinated patients and to non-vaccinated patients. Demographics, cycle characteristics and cycle outcomes were compared between groups. A total of 132 in-treatment vaccinated patients (study group), 132 pre-treatment vaccinated and 132 non-vaccinated patients that underwent fresh IVF cycles were included. Mean time from vaccination to retrieval in the study group was 6.68 days (SD 3.74; range 0-12). Oocyte yield was similar between groups (9.35 versus10.22 and 10.05 respectively; p=0.491). A linear regression model demonstrated no effect of vaccination before or during the stimulation, on oocyte yield (p>0.999). Clinical pregnancy rates (30 % versus 30 % versus 28 %) and ongoing pregnancy rates (25 % for all groups) did not differ between groups. In a logistic regression model for clinical pregnancy rates, vaccine administration and timing of vaccination were not a significant factor. This is the first study reporting the outcome of the mRNA BNT162b2 vaccine administration during the IVF stimulation itself. The vaccine administration had no impact on fresh IVF treatment outcomes compared to pre-treatment vaccinated or non-vaccinated patients. This adds to the growing evidence of COVID-19 vaccine safety in relation to fertility treatments and enables more flexibility regarding timing of vaccine administration.

The impact and inflammatory characteristics of SARS-CoV-2 infection during ovarian stimulation on the outcomes of assisted reproductive treatment

Introduction

Despite the global prevalence of coronavirus disease 2019 (COVID-19), limited research has been conducted on the effects of SARS-CoV-2 infection on human reproduction. The aims of this study were to investigate the impact of SARS-CoV-2 infection during controlled ovarian stimulation (COS) on the outcomes of assisted reproductive treatment (ART) and the cytokine status of patients.

Methods

This retrospective cohort study included 202 couples who received ART treatment, 101 couples infected with SARS-CoV-2 during COS and 101 matched uninfected couples. The parameters of ovarian stimulation and pregnancy outcomes were compared between the two groups. The All-Human Inflammation Array Q3 kit was utilized to measure cytokine levels in both blood and follicular fluid.

Results

No difference was found in the number of good-quality embryos (3.3 ± 3.1 vs. 3.0 ± 2.2, P = 0.553) between the infected and uninfected groups. Among couples who received fresh embryo transfers, no difference was observed in clinical pregnancy rate (53.3% vs. 51.5%, P = 0.907). The rates of fertilization, implantation, miscarriage, ectopic pregnancy and live birth were also comparable between the two groups. After adjustments were made for confounders, regression models indicated that the quality of embryos (B = 0.16, P = 0.605) and clinical pregnancy rate (P = 0.206) remained unaffected by SARS-CoV-2 infection. The serum levels of MCP-1, TIMP-1, I-309, TNF-RI and TNF-RII were increased, while that of eotaxin-2 was decreased in COVID-19 patients. No significant difference was found in the levels of cytokines in follicular fluid between the two groups.

Conclusion

Asymptomatic or mild COVID-19 during COS had no adverse effects on ART outcomes. Although mild inflammation was present in the serum, it was not detected in the follicular fluid of these patients. The subsequent immune response needs further investigation.

Prolongation of the Menstrual Cycle After Receipt of the Primary Series and Booster Doses of mRNA Coronavirus Disease 2019 (COVID-19) Vaccination

OBJECTIVE

To quantitatively evaluate the effect of a booster vaccination dose against coronavirus disease 2019 (COVID-19) on menstrual cycle in a large-scale retrospective cohort study using a menstrual cycle tracking smartphone application (app).

METHODS

Prospectively or retrospectively recorded data, including the start and finish dates of menstrual cycles, were collected with the app. Detailed data on vaccinations, side effects, and participants' characteristics were retrospectively collected from a questionnaire on the app. For each COVID-19 vaccination shot (first, second, and third), within-individual changes in menstrual cycle length up to the fourth postvaccination cycle were evaluated.

RESULTS

Among the 7,376 and 6,873 participants who had the first and second COVID-19 vaccine doses in different menstrual cycles, respectively, menstrual cycles immediately after the vaccination (first postvaccination cycles) were an average of 0.22 days (95% CI, 0.06-0.39) and 0.37 days (95% CI, 0.20-0.54) longer than the prevaccination cycle. In contrast, among the 1,672 participants who received the first and second doses in the same cycle, the first postvaccination cycle was an average of 4.21 days (95% CI, 3.69-4.72) longer. The second to fourth postvaccination cycles returned to the level of the prevaccination cycle. However, among the 4,768 participants who had the third COVID-19 vaccine dose, the menstrual cycle immediately after the vaccination was an average of 1.20 days (95% CI, 1.00-1.40) longer, with prolongation of cycles of 0.27 days (95% CI, 0.10-0.44) to 0.41 days (95% CI, 0.22-0.59) persisting from the second to the fourth postvaccination cycle.

CONCLUSION

The booster shot against COVID-19 may have a greater and longer-lasting effect on menstrual cycles than the primary-series shots. Although the effect size was small, evidence on the side effects of immunization on menstruation should be accumulated.

Effects of COVID-19 vaccination on human fertility: a post-pandemic literature review

Although vaccination with the Coronavirus disease 2019 vaccine is important and effective in the prevention of SARS-CoV-2 infection, the public expressed concerns regarding the adverse effects of vaccine on fertility. Some reviews have focused on it, they have been unable to collect sufficient research data because of the earlier publication period. As relevant evidence has gradually increased, we reviewed these studies from the perspectives of males, females with or without pregnancy, and different vaccine types. The results suggest that although males may experience fluctuations in semen parameters within their physiological ranges after receiving the vaccine, it has not yet reached a level of influence on the partner's pregnancy probability. As to female without pregnancy, it is believed that vaccination will not affect fertility; however, more research is needed to explore the short-term impact. Vaccination during any trimester is considered safe in pregnant women.

Comprehensive evaluation of the effect of inactivated SARS-CoV-2 vaccination on female fertility: A retrospective cohort study

Fear of possible negative effects of coronavirus disease 2019 (COVID-19) vaccine on fertility is the main reason for vaccine hesitancy among the public especially women of childbearing age. Despite the high coverage of COVID-19 vaccination in China, more scientific evidence is still needed to address their concerns and guide fertility counseling and management in the future. Herein, we performed a retrospective cohort study at a single large center for reproductive medicine in China between August 2020 and May 2023. Patients aged 20-42 years with no history of laboratory-confirmed COVID-19 were included and categorized into different groups according to their vaccination status. The serum sex hormone levels, anti-Müllerian hormone concentrations, embryo quality, and pregnancy outcomes were evaluated and compared among them. We found there were no significant differences in the concentrations of follicle-stimulating hormone, luteinizing hormone and progesterone between the unvaccinated, first-dose, second-dose, and booster vaccinated groups. However, the estradiol showed a highly significant increase in the one-dose vaccinated group compared with its levels in other groups. Among unvaccinated and either vaccinated patients, anti-Müllerian hormone levels were comparable (p = 0.139). The number of oocytes retrieved, fertilization rate and good-quality embryo rate were all similar between each group of in vitro fertilization and intracytoplasmic sperm injection. No significant differences were observed regarding other laboratory parameters. Moreover, the vaccination status of infertile couples did not exert any adverse effect on the pregnancy outcomes in all assisted reproductive technologies cycles. In short, we comprehensively evaluated the reproductive safety of inactivated severe acute respiratory syndrome coronavirus 2 vaccine and found any dose of vaccination wouldn't negatively affect female fertility parameters such as sex hormone levels and ovarian reserve. Moreover, this is the first study to complete the live birth follow-up of the cohort after receiving inactivated severe acute respiratory syndrome coronavirus 2 vaccine, further dispelling the misconception and providing reassurance for decision-making by clinicians.

Impact of inactivated COVID-19 vaccination on female ovarian reserve: a propensity score-matched retrospective cohort study

Purpose

To explore the impact of inactivated COVID-19 vaccination on ovarian reserve as assessed by serum anti-Müllerian hormone (AMH) concentration.

Methods

A total of 3160 women were included in this single-center retrospective cohort study between June 2021 and October 2022. Vaccination information were collected from official immunization records available in personal mobile apps. Serum AMH was qualified by electrochemiluminescence immunoassay and compared with previous measurement data within three years. Women were categorized to the vaccinated group if they received two doses of inactivated COVID-19 vaccines (Sinopharm or Sinovac) between AMH tests (n = 488), and to the control group if not vaccinated (n = 2672). Propensity score matching and multivariate linear regression were performed to control for potential confounders. The main outcome measures were the numeric AMH change and percentage AMH change between the two tests.

Results

There were 474 women left in each group after matching all baseline characteristics. The mean interval from the first to second AMH measurement was 508.0 ± 250.2 and 507.5 ± 253.6 days for vaccinated and unvaccinated women, respectively (P = 0.680). Both groups had a significant AMH decrease in the second test compared with the first test (P = 0.001). However, the second AMH level remained comparable between groups (3.26 ± 2.80 vs. 3.24 ± 2.61 ng/mL, P = 0.757). Similarly, no significant differences were observed in numerical (-0.14 ± 1.32 vs. -0.20 ± 1.56 ng/mL, P = 0.945) and percentage (2.33 ± 58.65 vs. 0.35 ± 48.42%, P = 0.777) AMH changes. The results were consistent in sub-analyses for women aged <35 and ≥35 years. There were also no significant differences when vaccinated women were divided according to the time interval after vaccination: ≤30, 31-60, 61-90, and ≥91 days.

Conclusion

Our study provides the first evidence that inactivated COVID-19 vaccination has no measurable detrimental effect on ovarian reserve, regardless of female age and vaccination interval. This reassuring finding adds to the safety evidence of COVID-19 vaccine in fertility, and should be useful to promote vaccine acceptance. Multicenter prospective cohort studies are needed to validate our conclusion.

COVID-19 Vaccines and Assisted Reproductive Techniques: A Systematic Review

Objective: To review the current knowledge concerning COVID-19 vaccination and assisted reproductive techniques (ART). Methods: A systematic review in Pubmed-Medline, the Cochrane Database, the Web of Science, and the National Guideline was performed. Studies were selected if they were primary studies, included vaccinated (case) and unvaccinated (control) patients, and described fertility treatment response. Results: A total of 24 studies were selected. Outcomes related to the association between COVID-19 vaccination and ART were collected. The vast majority of studies found no statistical differences concerning oocyte stimulation response, embryo quality, implantation rates, or pregnancy outcome (clinical or biochemical pregnancy rates and losses) when comparing cases and controls. Similarly, no differences were found when comparing different types of vaccines or distinct ART (artificial insemination, in vitro fertilization, and embryo transfer of frozen embryos). Conclusions: Patients receiving ART and health care professionals should be encouraged to complete and recommend COVID-19 vaccination, as the available evidence regarding assisted reproductive outcomes is reassuring.

COVID-19 vaccination and menstrual cycle characteristics: A prospective cohort study

We prospectively examined the association between COVID-19 vaccination and menstrual cycle characteristics in an internet-based prospective cohort study. We included a sample of 1,137 participants who enrolled in Pregnancy Study Online (PRESTO), a preconception cohort study of couples trying to conceive, during January 2021-August 2022. Eligible participants were aged 21-45 years, United States or Canadian residents, and trying to conceive without fertility treatment. At baseline and every 8 weeks for up to 12 months, participants completed questionnaires on which they provided information on COVID-19 vaccination and menstrual cycle characteristics, including cycle regularity, cycle length, bleed length, heaviness of bleed, and menstrual pain. We fit generalized estimating equation (GEE) models with a log link function and Poisson distribution to estimate the adjusted risk ratio (RR) for irregular cycles associated with COVID-19 vaccination. We used linear regression with GEE to estimate adjusted mean differences in menstrual cycle length associated with COVID-19 vaccination. We adjusted for sociodemographic, lifestyle, medical and reproductive factors. Participants had 1.1 day longer menstrual cycles after receiving the first dose of COVID-19 vaccine (95 % CI: 0.4, 1.9) and 1.3 day longer cycles after receiving the second dose (95 % CI: 0.2, 2.5). Associations were attenuated at the second cycle post-vaccination. We did not observe strong associations between COVID-19 vaccination and cycle regularity, bleed length, heaviness of bleed, or menstrual pain. In conclusion, COVID-19 vaccination was associated with a ∼1 day temporary increase in menstrual cycle length, but was not appreciably associated with other menstrual cycle characteristics.

Female reproduction and abnormal uterine bleeding after COVID-19 vaccination

Coronavirus disease 2019 (COVID-19) vaccines have been widely administered throughout the global community to minimize the morbidity and mortality caused by the COVID-19 pandemic. Although generally well-tolerated, these vaccines have generated some unwanted consequences, including thrombosis and menstrual irregularities. The effect of vaccination on female reproductive function has also been questioned. The aim of this review is to give readers a clear understanding of the effects of COVID-19 vaccines on thrombosis, reproductive function, and menstrual irregularities by systemically analyzing the available literature. The available evidence suggests that COVID-19 vaccines have a minimal impact on ovarian reserve. Furthermore, in vitro fertilization outcomes after COVID-19 vaccination remain unimpaired compared to those who did not receive the vaccines. Current evidence supports a certain degree of impact of COVID-19 vaccines on the menstrual cycle, with the most frequent alteration being menstrual irregularity, followed by menorrhagia. These changes are generally well-tolerated and transient, lasting less than 2 months. This review, by providing information with up-to-date references on this issue, may enhance readers' understanding of the impact of COVID-19 vaccines on female reproductive function and the menstrual cycle.

The risk of miscarriage following COVID-19 vaccination: a systematic review and meta-analysis

STUDY QUESTION

What is the risk of miscarriage among pregnant women who received any of the COVID-19 vaccines?

SUMMARY ANSWER

There is no evidence that COVID-19 vaccines are associated with an increased risk of miscarriage.

WHAT IS KNOWN ALREADY

In response to the COVID-19 pandemic, the mass roll-out of vaccines helped to boost herd immunity and reduced hospital admissions, morbidity, and mortality. Still, many were concerned about the safety of vaccines for pregnancy, which may have limited their uptake among pregnant women and those planning a pregnancy.

STUDY DESIGN, SIZE, DURATION

For this systematic review and meta-analysis, we searched MEDLINE, EMBASE, and Cochrane CENTRAL from inception until June 2022 using a combination of keywords and MeSH terms.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We included observational and interventional studies that enrolled pregnant women and evaluated any of the available COVID-19 vaccines compared to placebo or no vaccination. We primarily reported on miscarriage in addition to ongoing pregnancy and/or live birth.

MAIN RESULTS AND THE ROLE OF CHANCE

We included data from 21 studies (5 randomized trials and 16 observational studies) reporting on 149 685 women. The pooled rate of miscarriage among women who received a COVID-19 vaccine was 9% (n = 14 749/123 185, 95% CI 0.05-0.14). Compared to those who received a placebo or no vaccination, women who received a COVID-19 vaccine did not have a higher risk of miscarriage (risk ratio (RR) 1.07, 95% CI 0.89-1.28, I2 35.8%) and had comparable rates for ongoing pregnancy or live birth (RR 1.00, 95% CI 0.97-1.03, I2 10.72%).

LIMITATIONS, REASONS FOR CAUTION

Our analysis was limited to observational evidence with varied reporting, high heterogeneity and risk of bias across included studies, which may limit the generalizability and confidence in our findings.

WIDER IMPLICATIONS OF THE FINDINGS

COVID-19 vaccines are not associated with an increase in the risk of miscarriage or reduced rates of ongoing pregnancy or live birth among women of reproductive age. The current evidence remains limited and larger population studies are needed to further evaluate the effectiveness and safety of COVID-19 vaccination in pregnancy.

STUDY FUNDING/COMPETING INTEREST(S)

No direct funding was provided to support this work. M.P.R. was funded by the Medical Research Council Centre for Reproductive Health Grant No: MR/N022556/1. B.H.A.W. hold a personal development award from the National Institute of Health Research in the UK. All authors declare no conflict of interest.

REGISTRATION NUMBER

CRD42021289098.

Effect of female coronavirus disease 2019 vaccination on assisted reproductive outcomes: a systematic review and meta-analysis

IMPORTANCE

The effect of coronavirus disease 2019 (COVID-19) vaccination on fertility warrants clarification in women undergoing assisted reproductive treatment.

OBJECTIVE

To study the association between female COVID-19 vaccination and outcomes of assisted reproductive treatment.

DATA SOURCES

PubMed, Embase, the Web of Science, Cochrane Library, and medRxiv and bioRxiv were searched for eligible studies from December 1, 2019, to November 30, 2022, with no language restrictions.

STUDY SELECTION AND SYNTHESIS

Observational studies comparing assisted reproductive outcomes between women with and without COVID-19 vaccination were included. The pooled estimates were calculated using the random-effects models as mean differences (MDs), standardized MDs, or odds ratios with 95% confidence intervals (CIs). Heterogeneity was evaluated using the I2 statistic.

MAIN OUTCOMES

The number of oocytes retrieved and clinical pregnancy rate.

RESULTS

Twenty-one cohort studies involving a total of 19,687 treatment cycles were included. In a comparison of the vaccinated vs. unvaccinated groups, the pooled MD for oocyte number was -0.06 (95% CI, -0.51 to 0.39; I2 = 0), and the pooled odds ratio for clinical pregnancy was 0.95 (95% CI, 0.85-1.05; I2 = 0). Similarly, there were no statistically significant adverse effects identified in other outcomes determined a priori, including 4 cycle characteristics, 6 laboratory parameters, and 3 pregnancy indicators. Most results were consistently unchanged in subgroup and sensitivity analyses, with no evidence of publication bias according to Egger's test.

CONCLUSION AND RELEVANCE

Our work did not find significant differences in assisted reproductive outcomes between vaccinated and unvaccinated women. However, more data are warranted to confirm the safety of COVID-19 vaccination for assisted reproductive treatment and in female fertility in general.

Effect of COVID-19 vaccination on the outcome of in vitro fertilization: A systematic review and meta-analysis

Background

Universal COVID-19 vaccination programs are now recommended in several countries and represent the most effective preventive measure against COVID-19. However, some reports suggest that vaccination may cause infertility or have adverse effects on pregnancy. Conflicting reports have led to vaccine hesitancy in women planning pregnancy.

Purpose

To determine whether vaccination against COVID-19 affects in vitro fertilization (IVF) outcomes, we conducted a meta-analysis.

Method

A systematic search was conducted using PubMed, Embase, MEDLINE, and Web of Science databases for all published literature on COVID-19 vaccines and outcomes of IVF. International Prospective Register of Systematic Reviews registration was completed on September 13, 2022 (CRD42022359771).

Results

We analyzed 20 studies totaling 18,877 individual cases undergoing IVF. COVID-19 vaccination had significant effect on clinical and ongoing pregnancy rate (risk ratio (RR): 0.97; 95% confidence interval (CI): 0.94–0.99; RR: 0.93; 95% CI: 0.87–0.99). These outcomes did not differ between vaccinated and unvaccinated individuals: biochemical pregnancy rate (RR: 0.95; 95% CI: 0.88–1.03), implantation rate (RR: 1.02; 95%CI: 0.97–1.07; P = 0.41), the number of oocytes (mean difference (MD): 0.12; 95% CI: −0.65–0.88) and MII/mature oocytes recovered (MD: 0.27; 95% CI: −0.36–0.90), blastocysts rate (MD: 0.01; 95% CI: −0.04, 0.06), and fertilization rate (MD: 1.08; 95% CI: −0.57, 2.73).

Conclusion

Our findings suggest that vaccination against COVID-19 does not adversely affect the biochemical pregnancy rates; number of oocytes and MII/mature oocytes obtained; implantation, blastocysts; and fertilization rates in women undergoing IVF treatment. Subgroup analysis showed that the mRNA vaccine had no statistical significance on all indexes (clinical, biochemical, or ongoing pregnancy rates; implantation, blastocysts, or fertilization rates; and the number of oocytes and MII/mature oocytes). The findings of this meta-analysis are anticipated to increase the willingness of women planning IVF treatment to receive COVID-19 vaccination and provide evidence-based medical guidance for the development and implementation of guidelines.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, identifier: CRD42022359771.

SARS-CoV-2, fertility and assisted reproduction

BACKGROUND

In 2020, SARS-CoV-2 and the COVID-19 pandemic had a huge impact on the access to and provision of ART treatments. Gradually, knowledge of the virus and its transmission has become available, allowing ART activities to resume. Still, questions on the impact of the virus on human gametes and fertility remain.

OBJECTIVE AND RATIONALE

This article summarizes published data, aiming to clarify the impact of SARS-CoV-2 and the COVID-19 disease on human fertility and assisted reproduction, as well as the impact of vaccination, and from this, provide answers to questions that are relevant for people contemplating pregnancy and for health care professionals.

SEARCH METHODS

PUBMED/MEDLINE and the WHO COVID-19 database were searched from inception to 5 October 2022 with search terms focusing on 'SARS-CoV-2' and gametes, embryos, reproductive function, fertility and ART. Non-English studies and papers published prior to 2020 were excluded, as well as reviews and non-peer reviewed publications. Full papers were assessed for relevance and quality, where feasible.

OUTCOMES

From the 148 papers included, the following observations were made. The SARS-CoV-2-binding proteins, angiotensin-converting enzyme 2 (ACE2) and type II transmembrane serine protease (TMPRSS2), are expressed in the testis, but co-expression remains to be proven. There is some evidence of SARS-CoV-2 RNA in the ejaculate of COVID-19 patients with severe disease, but not in those with mild/moderate disease. SARS-CoV-2 infection can impair spermatogenesis, but this seems to resolve after one spermatogenic cycle. Testosterone levels seem to be lower during and after COVID-19, but long-term data are lacking; disease severity may be associated with testosterone levels. COVID-19 cannot be considered a sexually transmitted disease. There is no co-expression of ACE2 and TMPRSS2 in the myometrium, uterus, ovaries or fallopian tubes. Oocytes seem to have the receptors and protease machinery to be susceptible to SARS-CoV-2 infection; however, viral RNA in oocytes has not been detected so far. Women contemplating pregnancy following COVID-19 may benefit from screening for thyroid dysfunction. There is a possible (transient) impact of COVID-19 on menstrual patterns. Embryos, and particularly late blastocysts, seem to have the machinery to be susceptible to SARS-CoV-2 infection. Most studies have not reported a significant impact of COVID-19 on ovarian reserve, ovarian function or follicular fluid parameters. Previous asymptomatic or mild SARS-CoV-2 infection in females does not seem to negatively affect laboratory and clinical outcomes of ART. There are no data on the minimum required interval, if any, between COVID-19 recovery and ART. There is no evidence of a negative effect of SARS-CoV-2 vaccination on semen parameters or spermatogenesis, ovarian function, ovarian reserve or folliculogenesis. A transient effect on the menstrual cycle has been documented. Despite concerns, cross reactivity between anti-SARS-CoV-2 spike protein antibodies and Syncytin-1, an essential protein in human implantation, is absent. There is no influence of mRNA SARS-CoV-2 vaccine on patients' performance during their immediate subsequent ART cycle. Pregnancy rates post-vaccination are similar to those in unvaccinated patients.

WIDER IMPLICATIONS

This review highlights existing knowledge on the impact of SARS-CoV-2 infection or COVID-19 on fertility and assisted reproduction, but also identifies gaps and offers suggestions for future research. The knowledge presented should help to provide evidence-based advice for practitioners and couples contemplating pregnancy alike, facilitating informed decision-making in an environment of significant emotional turmoil.

Safety of COVID-19 vaccination in women undergoing IVF/ICSI treatment - Clinical study and systematic review

Background

It was suggested that vaccination in general might affect reproductive health. Safety of COVID-19 vaccination in women undergoing assisted reproductive techniques (ART) treatment is not well established.

Methods

We performed a retrospective study including 536 women undergoing fresh embryo transfer after IVF/ICSI treatment in a huge IVF center in southern China to investigate the effect of COVID-19 vaccination on oocyte maturation, fertilization rate, blastulation rate, implantation rate, clinical pregnancy rate and miscarriage rate. In addition, we performed a systematic review of existing studies on the safety of COVID-19 vaccination in women undergoing ART treatment.

Results

In our study, 268 women received inactivated or recombinant COVID-19 vaccination and 268 controls were enrolled based on propensity score matching. We observed a decreased fertilization rate and signs for impaired oocyte maturation in vaccinated women. Besides our study, there were 15 studies analyzing the safety of COVID-19 vaccination in women undergoing ART treatment. For the mRNA vaccines, no adverse signals were reported concerning oocyte maturation, fertilization rate, blastulation rate, implantation rate, clinical pregnancy rate and miscarriage rate. In women being vaccinated with an inactivated vaccine, implantation rate, clinical pregnancy rate and miscarriage rate were not affected, whereas oocyte maturation and fertilization rate were impaired.

Conclusions

Vaccination against COVID-19 in women undergoing ART treatment seems to be safe especially for women getting mRNA vaccines. The effects on oocyte maturation and fertilization rate of inactivated and recombinant COVID-19 vaccinations might be a safety signal and need further investigation and independent confirmation.

Does mRNA COVID-19 vaccination in oocyte donors impact ovarian stimulation parameters or IVF outcomes for recipients?

RESEARCH QUESTION

What is the effect of mRNA severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination in young oocyte donors in terms of ovarian response to stimulation, fertilization rate, embryo development and clinical outcomes in recipients?

DESIGN

This retrospective, multicentre cohort study evaluated 115 oocyte donors who had undergone at least two ovarian stimulation protocols (before and after complete SARS-CoV-2 vaccination) between November 2021 and February 2022. Comparisons were made of the primary outcomes of days of stimulation, total dose of gonadotrophins and laboratory performance in ovarian stimulation in oocyte donors before and after vaccination. A total of 136 cycles in matched recipients were analysed as secondary outcomes and, from those, 110 women received a fresh single-embryo transfer, with analysis of biochemical β-human chorionic gonadotrophin concentrations and rates of clinical pregnancy with heartbeat.

RESULTS

Longer stimulation was required in the post-vaccination than pre-vaccination group (10.31 ± 1.5 versus 9.51 ± 1.5 days; P < 0.001) along with higher gonadotrophin consumption (2453.5 ± 740 versus 2235.5 ± 615 IU; P < 0.001) with a similar starting dose of gonadotrophins in both groups. More oocytes were retrieved in the post-vaccination group (16.62 ± 7.1 versus 15.38 ± 7.0; P = 0.02). However, the number of metaphase II (MII) oocytes was similar between groups (pre-vaccination 12.61 ± 5.9 versus post-vaccination 13.01 ± 6.6; P = 0.39) and the ratio of MII/retrieved oocytes favoured the pre-vaccination group (0.83 ± 0.1 versus 0.77 ± 0.2 post-vaccination; P = 0.019). In recipients with a similar number of provided oocytes, the fertilization rate, total number of obtained blastocysts, number of top-quality blastocysts, and rates of biochemical pregnancy and clinical pregnancy with heartbeat were not significantly different between groups.

CONCLUSIONS

This study shows no adverse influence of mRNA SARS-CoV-2 vaccination on ovarian response in a young population.

COVID-19 infection and vaccine have no impact on in-vitro fertilization (IVF) outcome

To investigate the effect of COVID-19 infection or vaccine on IVF outcome. This is a multicenter retrospective study. Data were collected from all patients treated in the ART units between September and November 2021 after the vaccination of the general population began. Medical records of all patients who had IVF/intracytoplasmic sperm injection (ICSI) were retrospectively reviewed. Patients were categorized into four groups: previously infected by COVID-19, vaccinated by COVID vaccine, previously infected and vaccinated, or neither infected nor vaccinated. Total number of participants 151 (vaccinated only 66, infected only 18, vaccinated and previously infected 34, and control 33. Outcomes (ET on day of trigger, number of oocytes retrieved, quality of oocytes, number of fertilized oocytes, number and quality of embryos, number of embryos transferred, number of embryos frozen, implantation rate and clinical pregnancy rate) were compared between these four groups. Moreover, we compared the outcome before and post infection, as well as before and post vaccine in a group of patients. No evidence was found to suggest that COVID-19 disease or SARS-CoV-2 Vaccine adversely affects Clinical pregnancy rates (positive fetal heartbeat) (OR 0.9, CI 0.5-1.9, OR 1.8, CI 0.9-3.6, respectively) and the following parameters: fertilization rate, implantation rate, positive bHcg) (OR 0.9, CI 0.5-1.8, OR 1.5, CI 0.7-2.9, respectively). Although a limitation of our study is the small comparison groups, and the wide confidence intervals in the Odds Ratio estimates.

The impact of maternal SARS-CoV-2 infection and COVID-19 vaccination on maternal-fetal outcomes

The rapidly evolving COVID-19 pandemic has resulted in an upsurge of scientific productivity to help address the global health crisis. One area of active research is the impact of COVID-19 on pregnancy. Here, we provide an epidemiological overview about what is known about the effects of maternal SARS-CoV-2 infection and COVID-19 vaccination on maternal-fetal outcomes, and identify gaps in knowledge. Pregnant people are at increased risk for severe COVID-19, and maternal SARS-CoV-2 infection increases the risk of negative maternal-fetal outcomes. Despite this elevated risk, there have been high rates of vaccine hesitancy, heightened by the initial lack of safety and efficacy data for COVID-19 vaccination in pregnancy. In response, retrospective cohort studies were performed to examine the impact of COVID-19 vaccination during pregnancy. Here, we report the vaccine's efficacy during pregnancy and its impact on maternal-fetal outcomes, as well as an overview of initial studies on booster shots in pregnancy. We found that pregnant people are at risk for more severe COVID-19 outcomes, maternal SARS-CoV-2 infection is associated with worse birth outcomes, COVID-19 vaccine hesitancy remains prevalent in the pregnant population, and COVID-19 vaccination and boosters promote better maternal-fetal outcomes. The results should help reduce vaccine hesitancy by alleviating concerns about the safety and efficacy of administering the COVID-19 vaccine during pregnancy. Overall, this review provides an introduction to COVID-19 during pregnancy. It is expected to help consolidate current knowledge, accelerate research of COVID-19 during pregnancy and inform clinical, policy, and research decisions regarding COVID-19 vaccination in pregnant people.

Inactivated Covid-19 vaccine did not undermine live birth and neonatal outcomes of women with frozen-thawed embryo transfer

STUDY QUESTION

Does inoculation with inactivated vaccines against coronavirus disease 2019 (Covid-19) before frozen-thawed embryo transfer (FET) affect live birth and neonatal outcomes?

SUMMARY ANSWER

Inactivated Covid-19 vaccines did not undermine live birth and neonatal outcomes of women planning for FET.

WHAT IS KNOWN ALREADY

Accumulating reports are now available indicating the safe use of mRNA vaccines against Covid-19 in pregnant and lactating women, and a few reports indicate that they are not associated with adverse effects on ovarian stimulation or early pregnancy outcomes following IVF. Evidence about the safety of inactivated Covid-19 vaccines is very limited.

STUDY DESIGN, SIZE, DURATION

This is a retrospective cohort analysis from Reproductive Medical Center of a tertiary teaching hospital. Clinical records and vaccination record of 2574 couples with embryos transferred between 1 March 2021 and 30 September 2021 were screened for eligibility of this study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Clinical and vaccination data of infertile couples planning for FET were screened for eligibility of the study. The reproductive and neonatal outcomes of FET women inoculated with inactivated Covid-19 vaccines or not were compared. The primary outcomes were live birth rate per embryo transfer cycle and newborns' birth height and weight. Secondary outcomes included rates of ongoing pregnancy, clinical pregnancy, biochemical pregnancy and spontaneous miscarriage. Multivariate logistical regression and propensity score matching (PSM) analyses were performed to minimize the influence of confounding factors. Subgroup analyses, including single dose versus double dose of the vaccines and the time intervals between the first vaccination and embryo transfer, were also performed.

MAIN RESULTS AND THE ROLE OF CHANCE

Vaccinated women have comparable live birth rates (43.6% versus 45.0% before PSM, P = 0.590; and 42.9% versus 43.9% after PSM, P = 0.688), ongoing pregnancy rates (48.2% versus 48.1% before PSM, P = 0.980; and 52.2% versus 52.7% after PSM, P = 0.875) and clinical pregnancy rate (55.0% versus 54.8% before PSM, P = 0.928; and 54.7% versus 54.2% after PSM, P = 0.868) when compared with unvaccinated counterparts. The newborns' birth length (50.0 ± 1.6 versus 49.0 ± 2.9 cm before PSM, P = 0.116; and 49.9 ± 1.7 versus 49.3 ± 2.6 cm after PSM, P = 0.141) and birth weight (3111.2 ± 349.9 versus 3030.3 ± 588.5 g before PSM, P = 0.544; and 3053.8 ± 372.5 versus 3039.2 ± 496.8 g after PSM, P = 0.347) were all similar between the two groups. Neither single dose nor double dose of vaccines, as well as different intervals between vaccination and embryo transfer showed any significant impacts on reproductive and neonatal outcomes.

LIMITATIONS, REASONS FOR CAUTION

The main findings might be limited by retrospective design. Besides, inoculations of triple dose of Covid-19 vaccines were not available by the time of data collection, thus the results cannot reflect the safe use of triple dose of inactivated Covid-19 vaccines. Finally, history of Covid-19 infection was based on patients' self-report rather than objective laboratory tests.

WIDER IMPLICATIONS OF THE FINDINGS

Eligible individuals of inactivated vaccines against Covid-19 should not postpone vaccination plan because of their embryo transfer schedule, or vice versa.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the Medical Key Discipline of Guangzhou (2021-2023). All authors had nothing to disclose.

TRIAL REGISTRATION NUMBER

N/A.

The impact of COVID-19 vaccines on fertility-A systematic review and meta-analysis

BACKGROUND

Despite literature's evidence about COVID-19 vaccines' safety, concerns have arisen regarding adverse events, including the possible impact on fertility, accentuated by misinformation and anti-vaccine campaigns. The present study aims to answer the question: Is there any impact of COVID-19 vaccines on the fertility of men and women of reproductive age?

METHODS

PubMed, Scopus, Web of Science, Cochrane and Embase databases were searched for eligible studies until June 8th, 2022. The search was restricted to articles regarding humans, published in any languages, without additional restrictions. Studies' quality was assessed by the Newcastle-Ottawa and the Before and After Quality Assessment scales for cohort and pre-post studies, respectively. Random-effect meta-analyses were performed for parameters considered in ≥ 2 studies, calculating means, p-values and 95 % Confidence Intervals (CIs).

RESULTS

Out of 1406 studies screened, 29 were included in the systematic review. These studies, conducted in Israel (34.5 %), USA (24.1 %), Russia (20.7 %) China (10.3 %), Italy (3.5 %), North America (3.5%) and Turkey (3.5 %) were of poor (34.5 %), moderate (58.6 %) and good (6.9 %) quality. Meta-analyses were performed for pre- and post-vaccination sperm progressive motility (44 %, 95 % CI 42 %-62 % vs 43 %, 95 % CI 31 %-59 % p = 0.07) and concentration (50.6 mln/ml, 95 % CI 35.1-72.8 vs 55.4 mln/ml, 95 % CI 37.4-82.2p = 0.12). Biochemical (0.51, 95 % CI 0.40-0.66 vs 0.60, 95 % CI 0.53-0.68p = 0.45) and clinical (0.45, 95 % CI 0.37-0.54 vs 0.47, 95 % CI 0.40-0.55 p = 0.31) pregnancy rate did not differ among vaccinated and not vaccinated groups. Subgroup meta-analyses based on the type of vaccine showed no significant difference: between vaccinated with mRNA vaccines and non-vaccinated regarding biochemical pregnancy rates; pre- and post-vaccination with Gam-COVID-Vac regarding testosterone, FSH and LH levels; pre- and post-vaccination with BNT162b2 vaccines regarding sperm volumes.

CONCLUSION

Based on the studies published so far, there is no scientific proof of any association between COVID-19 vaccines and fertility impairment in men or women.

Association Between Time Interval from COVID-19 Vaccination to In Vitro Fertilization and Pregnancy Rate After Fresh Embryo Transfer

IMPORTANCE

There is a lack of information regarding the need to postpone conception after COVID-19 vaccination.

OBJECTIVE

To investigate the time interval between the first dose of inactivated COVID-19 vaccine and in vitro fertilization (IVF) treatment as well as the rate of pregnancy after a fresh embryo transfer.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study was conducted at a single public IVF center in China. Female patients aged 20 to 47 years and undergoing IVF treatment were consecutively registered from May 1 to December 22, 2021, with follow-up until March 31, 2022. Patients with SARS-CoV-2 infection before or during IVF treatment and those who underwent 2 or more IVF treatments, received the noninactivated or unknown COVID-19 vaccine, or did not have a fresh embryo transfer were excluded from this study.

EXPOSURES

The vaccinated group (subdivided into 4 subgroups of time interval from first vaccination to fertilization treatment: ≤30 days, 31-60 days, 61-90 days, and ≥91 days) and nonvaccinated group.

MAIN OUTCOMES AND MEASURES

Risk ratios (RRs) for the association between the time interval and ongoing pregnancy (pregnancy continued at least 12 weeks).

RESULTS

A total of 3052 female patients (mean [SD] age, 31.45 [3.96] years) undergoing IVF treatment were analyzed in this study. There were 667 vaccinated patients receiving IVF (35 were vaccinated ≤30 days, 58 were vaccinated 31-60 days, 105 were vaccinated 61-90 days, and 469 were vaccinated ≥91 days before fertilization treatment), and 2385 unvaccinated patients receiving treatment. The ovarian stimulation and laboratory parameters were similar among all groups. Ongoing pregnancy was significantly lower in the 30 days or less subgroup (34.3% [12 of 35]; adjusted RR [aRR], 0.61; 95% CI, 0.33-0.91) and the 31 to 60 days' subgroup (36.2% [21 of 58]; aRR, 0.63; 95% CI, 0.42-0.85). A slightly but not statistically lower rate was found in the 61 to 90 days' subgroup, and no reduced risk for ongoing pregnancy in the 91 days or more subgroup was observed (56.3% [264 of 469]; aRR, 0.96; 95% CI, 0.88-1.04) compared with the unvaccinated group (60.3% [1439 of 2385], as reference).

CONCLUSIONS AND RELEVANCE

Findings of this study suggest that receipt of the first inactivated COVID-19 vaccine dose 60 days or less before fertilization treatment is associated with a reduced rate of pregnancy. In patients undergoing IVF treatment with a fresh embryo transfer, the procedure may need to be delayed until at least 61 days after COVID-19 vaccination.

SARS-CoV-2 the ASIA virus (autoimmune/autoinflammatory syndrome induced by adjuvants), the risk of infertility and vaccine hesitancy

INTRODUCTION

COVID-19 has had a calamitous impact on the global community. The current death toll far exceeds 6 million and large numbers of patients are experiencing long-term medical and psychiatric morbidity from the infection. The immunopathology of severe COVID-19 is now better understood. In severely affected patients, there is a chaotic, destructive immune response triggered by SARS-CoV-2, where autoimmunity features prominently.

AREAS COVERED

COVID-19 vaccines ensure a coordinated, balanced immune response to future SARS-CoV-2 infection. The rapid global deployment of effective COVID-19 vaccines has been hindered by financial, logistical and political barriers. Of concern is increasing vaccine hesitancy caused by unfounded conspiracy theories of vaccine adverse effects, often fueled by misinformation and disinformation on social media.

EXPERT OPINION

This perspective discusses the potential impact of the so-called autoimmune/autoinflammatory syndrome caused by adjuvants (ASIA) on COVID-19 vaccine uptake. Proponents of the ASIA syndrome have inappropriately linked infertility to HPV vaccines and have recently suggested antigenic cross-reactivity between SARS-CoV-2 and ovarian follicles. COVID-19 vaccines have also been linked to ASIA and unfounded fear of infertility is a leading cause of vaccine hesitancy. Vaccine hesitancy caused by spurious disorders such as ASIA are likely to harm individuals and delay global vaccination efforts leading to emergence of vaccine and monoclonal antibody resistant mutants, thereby prolonging the COVID-19 pandemic.

Endocrine system after 2 years of COVID-19 vaccines: A narrative review of the literature

PURPOSE

The purpose of this study was to describe the current knowledge on the potential endocrine adverse effects post-COVID-19 vaccines.

METHODS

A PubMed/MEDLINE, Web of Science, and Scopus research was performed. Case reports, case series, original studies, and reviews written in English and published online up to 31 July 2022 were selected and reviewed. The final reference list was defined based on the relevance of each paper to the scope of this review.

RESULTS

The available data showed that endocrine side effects are generally rare and with favorable outcome, being thyroid disorders the most common. Conversely, data on type 1 diabetes mellitus are rare; adrenal and pituitary events are even anecdotal. Finally, the available clinical studies suggest no impact on female reproductive system and on male and couple fertility.

CONCLUSION

Overall, these data show that, after 2 years of COVID-19 vaccines, the endocrine system is not heavily threatened.