Effect of COVID-19 vaccination on the timing and flow of menstrual periods in two cohorts

Adverse Menstrual Events Reported After and Before (or Without) COVID-19 Vaccination: A Systematic Review and Meta-Analysis of Comparative Observational Studies

BACKGROUND

Reports of adverse menstrual events emerged during the COVID-19 vaccination campaign in multiple countries. This raised the question whether these reports were caused by the vaccines. The aim of this systematic review was to evaluate comparative studies on this topic (registered at PROSPERO [CRD42022324973]).

METHODS

We included observational studies such as cohort studies and surveys comparing the response to self-reported questionnaires between post- versus pre-vaccination data. PubMed and Cochrane Library searches were conducted on 1 September 2023. The primary outcome was the incidence of any prespecified adverse menstrual event, and the outcome measure was the risk ratio. The meta-analysis was conducted by using the Mantel-Haenszel method and the random effects model. We summarized the results on risk factors as well as key findings of the studies included.

RESULTS

We retrieved 161 references from electronic databases and additional sources such as references lists. Of those, we considered 21 comparative observational studies. The meta-analysis of any adverse menstrual adverse event reported in 12 studies resulted in a pooled estimate (risk ratio 1.13; 95% CI, 0.96-1.31) that did not favor any group. The analysis was constrained by considerable clinical and statistical heterogeneity. Risk factors for self-reported menstrual changes included a history of COVID-19 infection, the concern about COVID-19 vaccines, smoking, previous cycle irregularities, depression, and stress, and other issues.

CONCLUSIONS

The risk ratio did not favor any group and heterogeneity was prevalent among the studies. Most studies suggested that the reported changes were temporary, minor, and nonserious.

Clinical Spectrum of Long COVID: Effects on Female Reproductive Health

The COVID-19 pandemic caused by SARS-CoV-2 has presented numerous health challenges, including long-term COVID, which affects female reproductive health. This review consolidates the current research on the impact of SARS-CoV-2 on the menstrual cycle, ovarian function, fertility, and overall gynecological health. This study emphasizes the role of angiotensin-converting enzyme receptors in viral entry and the subsequent tissue-specific pathological effects. It also explores the potential influence of long COVID on hormonal balance and immune responses, contributing to menstrual irregularities and impaired ovarian function. The findings indicate a higher prevalence of long-term COVID-19 among women, highlighting the substantial implications for reproductive health and the need for sex-sensitive longitudinal studies. Enhanced surveillance and targeted research are essential to develop effective interventions that prioritize women's reproductive well-being following SARS-CoV-2 infection. This review advocates for a sex-informed approach to ongoing COVID-19 research and healthcare strategies, aiming to provide up-to-date and pertinent data for healthcare providers and the general public, ultimately improving outcomes for females affected by long COVID.

Association between COVID-19 vaccination and menstruation: a state of the science review

INTRODUCTION

Menstrual health is a key patient-reported outcome beyond its importance as a general indicator of health and fertility. However, menstrual function was not measured in the clinical trials of COVID-19 vaccines. The purpose of this review was to synthesise the existing literature on the relationship between COVID-19 vaccination and menstrual health outcomes.

METHODS

A PubMed search to 31 October 2023 identified a total of 53 publications: 11 prospective cohort studies, 11 retrospective cohort studies or registry-based cohort studies, and 31 cross-sectional or retrospective case-control studies.

RESULTS

Identified studies were generally at moderate-to-high risk of bias due to retrospective design, interviewer bias, and failure to include a non-vaccinated control group. Nonetheless, the bulk of the literature demonstrates that COVID-19 vaccine is associated with temporary changes in menstrual characteristics (cycle length and flow) and menstrual pain. Follicular phase (at the time of vaccination) is associated with greater increases in cycle length. Evidence suggests temporary post-vaccine menstrual changes in adolescents, abnormal vaginal bleeding in postmenopausal individuals, and a potential protective effect of using hormonal contraception.

CONCLUSIONS

In this review we found evidence supporting an association between the COVID-19 vaccine and menstrual health outcomes. Given the importance of menstrual function to overall health, we recommend that all future vaccine trials include menstruation as a study outcome. Future vaccine studies should include rigorous assessment of the menstrual cycle as an outcome variable to limit sources of bias, identify biological mechanisms, and elucidate the impact of stress.

The direct effect of SARS-CoV-2 virus vaccination on human ovarian granulosa cells explains menstrual irregularities

Following administration of the SARS-CoV-2 vaccine, many women worldwide reported short-term menstrual irregularities. Although menstrual bleeding, "the fifth vital sign", is experienced by more than 300 million people on any given day worldwide, these changes were only partially studied. Irregular periods are important well beyond fertility and the discomfort they impose; they are associated with the risk of cardiovascular morbidity, chronic diseases, and premature mortality. Pre-clinical examination of the vaccine polymeric envelope indicates its accumulation in the ovaries. The somatic endocrine cells of the ovarian follicle - the granulosa cells (GCs)-participate in the strict hypothalamic-pituitary-ovarian (HPO) feedback loop that governs the menstrual cycle via endocrine and paracrine regulators, as AMH and Inhibins. We aimed to unravel the direct effect of the COVID-19 vaccine on GCs and link their post-vaccine activity to changes in menstrual patterns. Human primary GCs exposed in-vitro to the Pfizer COVID-19 vaccine BNT162b2, demonstrated no change in their viability but altered mRNA transcripts, specifically of the regulatory key factors: InhibinB was upregulated, whereas AMH was downregulated. We further examined pre- and post-vaccination blood samples from individual women and found a 2-3 folds change in the post-vaccination FSH/InhibinB protein level ratio, compared to their pre-vaccination values. This altered expression of InhibinB could significantly impact the HPO axis in vaccinated women and may ultimately influence the endometrium cyclicity, manifested clinically by the commonly reported changes in menstrual bleeding patterns.

Anti-COVID-19 Vaccination Alters the Menstrual Cycle and Dose Accumulation Enhances the Effect

Background and Objectives: New investigations have detected an enhanced probability for women to develop menstrual cycle alterations after anti-COVID-19 vaccination. Moreover, given that the protective immunity provided by anti-COVID-19 vaccination appears to wane quickly, booster vaccination has been recommended. Nonetheless, whether adverse events arise from such repeated immunization has not been studied. Materials and Methods: We studied the incidence of menstrual cycle alterations, the quantity of menstrual cycle alterations per subject, and of altered menstrual cycles in nonpregnant women of fertile age after anti-COVID-19 vaccination in a cohort of vaccinated female subjects by the means of a standardized questionary that was applied via telephone calls each month. Subjects that received up to four doses were studied for 6 months after each dose. We calculated the odds ratio for enhanced incidence, as well as quadratic functions for the tendencies. A sensitivity analysis excluding subjects taking hormonal birth control and those with polycystic ovary syndrome was performed. Results: Anti-COVID-19 vaccination enhanced the probability to develop menstrual cycle alterations (OR 1.52, CI at 95% 1.2-1.8, p < 0.0001) and, interestingly, such a tendency was enhanced when subjects received more doses (R2 = 0.91). Furthermore, the same trends repeated for the quantity of alterations per subject, and of altered cycles. Such an effect was further demonstrated to be independent upon the vaccine brand being applied, the birth control status, and the diagnosis of polycystic ovary syndrome. Conclusions: Vaccination is the most cost-effective measure for primary prevention and is considered to be safe. Nonetheless, in this article, we show data that suggest that repeated vaccination of adult female subjects may lead to an enhanced incidence of menstrual cycle-related adverse events, quantity of alterations per subject, and altered cycles. We therefore think that the development of new vaccine formulations that produce longer-lasting immunity is of paramount importance to reduce the potential for dose accumulation-dependent enhanced risk.

Saudi Women's Perception of the Effect of COVID-19 Infection and Vaccination on Menstrual Cycle Length

Background and Aim

This study was conducted in the Kingdom of Saudi Arabia to investigate the effects of the COVID-19 virus and the vaccine on menstrual periods. The data from this study would increase people's awareness of the impacts of the virus and its vaccines on menstrual periods and serve as a reference for further studies.

Materials and Methods

The data was collected through a web link where standardized close-ended questionnaires were distributed via several social media platforms in Saudi Arabia.

Results

The study included 691 respondents, with 411 women meeting the inclusion criteria. The majority of participants fell within the age range of 35-45, and 64% held at least a bachelor's degree. The Eastern region of Saudi Arabia had the highest percentage of participants, while the Northern region had the lowest. More than half of the participants were married, and 57% reported having been infected with COVID-19. The vast majority (99%) had received the COVID-19 vaccine, primarily the Pfizer/BioNTech vaccine. The study assessed the association between menstruation experience and symptoms in three situations: before infection or vaccination, after COVID-19 infection, and after vaccination. Differences were observed in the length of the menstrual cycle and flow, but no statistically significant differences were found for pelvic and back pain.

Conclusions

The result of this current study suggests that COVID-19 infection and/or vaccination has several effects on the menstrual cycle which changes in menses are minimal and transient.

COVID-19 (SARS-CoV-2) mRNA vaccination does not affect basal sex hormone levels (follicle-stimulating hormone, luteinizing hormone, estradiol) in reproductive-age women

OBJECTIVE

People vaccinated with the coronavirus disease 2019 (COVID-19) (severe acute respiratory syndrome coronavirus-2 [SARS-CoV-2]) mRNA vaccine have reported experiencing various adverse effects. For instance, reproductive-age women have presented with complaints of abnormal uterine bleeding or menstrual cycle changes. We speculated that differences in basal sex hormone levels before and after vaccination may be present in women who experienced irregular bleeding or menstrual cycle changes; thus, this study aimed to investigate the differences in basal sex hormone levels of women before and after two doses of SARS-CoV-2 mRNA vaccination.

METHODS

This retrospective study included patients who received SARS-CoV-2 mRNA vaccines between January 2021 and February 2022 at a single center. In an outpatient setting, patients were queried regarding their menstrual cycle, the date of SARS-CoV-2 mRNA vaccination, vaccination type, and vaccination side effects. Differences in basal hormone levels (menstrual cycle days 2-3, follicle-stimulating hormone [FSH], luteinizing hormone [LH], and estradiol) before and after vaccination were compared.

RESULTS

Among the 326 patients, patients with no laboratory records of the hormones were excluded. The median time interval between SARS-CoV-2 mRNA vaccination and the laboratory test day was 79 days (interquartile range, 44 to 127). A comparative analysis of these hormones before and after vaccination revealed no significant differences. Subgroup analyses based on age and reported adverse events also found no statistically significant differences.

CONCLUSION

This study showed no significant differences in basal hormone levels (FSH, LH, and estradiol) before and after SARS-CoV-2 mRNA vaccination.

Abnormal uterine bleeding diagnoses and care following COVID-19 vaccination

BACKGROUND

There is evidence suggesting that COVID-19 vaccination may be associated with small, transitory effects on uterine bleeding, possibly including menstrual timing, flow, and duration, in some individuals. However, changes in health care seeking, diagnosis, and workup for abnormal uterine bleeding in the COVID-19 vaccine era are less clear.

OBJECTIVE

This study aimed to assess the impact of COVID-19 vaccination on incident abnormal uterine bleeding diagnosis and diagnostic evaluation in a large integrated health system.

STUDY DESIGN

Using segmented regression, we assessed whether the availability of COVID-19 vaccines was associated with changes in monthly, population-based rates of incident abnormal uterine bleeding diagnoses relative to the prepandemic period in health system members aged 16 to 44 years who were not menopausal. We also compared clinical and demographic characteristics of patients diagnosed with incident abnormal uterine bleeding between December 2020 and October 13, 2021 by vaccination status (never vaccinated, vaccinated in the 60 days before diagnosis, vaccinated >60 days before diagnosis). Furthermore, we conducted detailed chart review of patients diagnosed with abnormal uterine bleeding within 1 to 60 days of COVID-19 vaccination in the same time period.

RESULTS

In monthly populations ranging from 79,000 to 85,000 female health system members, incidence of abnormal uterine bleeding diagnosis per 100,000 person-days ranged from 8.97 to 19.19. There was no significant change in the level or trend in the incidence of abnormal uterine bleeding diagnoses between the prepandemic (January 2019-January 2020) and post-COVID-19 vaccine (December 2020-December 2021) periods. A comparison of clinical characteristics of 2717 abnormal uterine bleeding cases by vaccination status suggested that abnormal bleeding among recently vaccinated patients was similar or less severe than abnormal bleeding among patients who had never been vaccinated or those vaccinated >60 days before. There were also significant differences in age and race of patients with incident abnormal uterine bleeding diagnoses by vaccination status (Ps<.02). Never-vaccinated patients were the youngest and those vaccinated >60 days before were the oldest. The proportion of patients who were Black/African American was highest among never-vaccinated patients, and the proportion of Asian patients was higher among vaccinated patients. Chart review of 114 confirmed postvaccination abnormal uterine bleeding cases diagnosed from December 2020 through October 13, 2021 found that the most common symptoms reported were changes in timing, duration, and volume of bleeding. Approximately one-third of cases received no diagnostic workup; 57% had no etiology for the bleeding documented in the electronic health record. In 12% of cases, the patient mentioned or asked about a possible link between their bleeding and their recent COVID-19 vaccine.

CONCLUSION

The availability of COVID-19 vaccination was not associated with a change in incidence of medically attended abnormal uterine bleeding in our population of over 79,000 female patients of reproductive age. In addition, among 2717 patients with abnormal uterine bleeding diagnoses in the period following COVID-19 vaccine availability, receipt of the vaccine was not associated with greater bleeding severity.

Impact of COVID-19 infections and vaccination on menstrual cycle symptoms in the south of Jordan: a cross-sectional study

BACKGROUND

Several recent studies have highlighted the need for more evaluation of the impact of COVID-19 infections and vaccines on the reproductive system and menstruation. This study aimed to assess the impact of COVID-19 infection and vaccines on menstrual symptoms.

METHODS

A cross-sectional survey utilizing face-to-face interviews from January 1 to 31 March 2022 was conducted in the city of Al-Karak in southern Jordan. The questionnaire included sociodemographic characteristics, medical and reproductive history, the contraceptive method used if any, menstrual cycle (MC) status, previous medical and drug history, and the impact of infection and vaccination on the MC.

RESULTS

The study questionnaire was completed by 400 participants with a mean age of 32.1±12.6 years. Regarding the history of COVID-19 infections, 33.8% of the participants reported a history of confirmed COVID-19 infections, 77.8% of them did not report any menstrual changes following the infection, while the remaining 22.2% reported changes in menstruation. The most commonly reported post-COVID-19 manifestations were irregular (27.6%) and light menstrual cycle (MC) (24.15) or dysmenorrhea (24.1%). Heavy menstruation was reported by 17.2% of participants post-COVID-19 infection. Two-thirds of the study participants (66.6%) reported no changes in the MC following the administration of the COVID-19 vaccine. The most reported symptoms for those who experienced changes in the MC following the vaccination were irregular cycle (13.1%), heavy menstruation (7%), and light menstruation (7%). Other reported symptoms were dysmenorrhea (4.6%), intermenstrual bleeding (1.2%), and amenorrhea (0.5%).

CONCLUSION

This study revealed minor changes in the MC following COVID-19 infections and administration of the COVID-19 vaccine. These findings are consistent with published reports. It is recommended that future clinical trials for new vaccines for women of childbearing age include outcomes related to sex hormones and MC. Women should be encouraged to take the vaccines and report symptoms to healthcare professionals for further assessment.

Timing of Coronavirus Disease 2019 (COVID-19) Vaccination and Effects on Menstrual Cycle Changes

OBJECTIVE

To assess whether menstrual cycle timing (follicular or luteal phase) of coronavirus disease 2019 (COVID-19) vaccine administration is associated with cycle length changes.

METHODS

We used prospectively collected (2021-2022) menstrual cycle tracking data from 19,497 reproductive-aged users of the application "Natural Cycles." We identified whether vaccine was delivered in the follicular or luteal phase and also included an unvaccinated control group. Our primary outcome was the adjusted within-individual change in cycle length (in days) from the average of the three menstrual cycles before the first vaccination cycle (individuals in the unvaccinated control group were assigned a notional vaccine date). We also assessed cycle length changes in the second vaccination cycle and whether a clinically significant change in cycle length (8 days or more) occurred in either cycle.

RESULTS

Most individuals were younger than age 35 years (80.1%) and from North America (28.6%), continental Europe (33.5%), or the United Kingdom (31.7%). In the vaccinated group, the majority received an mRNA vaccine (63.8% of the full sample). Individuals vaccinated in the follicular phase experienced an average 1-day longer adjusted cycle length with a first or second dose of COVID-19 vaccine compared with their prevaccination average (first dose: 1.00 day [98.75% CI, 0.88-1.13], second dose: 1.11 days [98.75% CI, 0.93-1.29]); those vaccinated in the luteal phase and those in the unvaccinated control group experienced no change in cycle length (respectively, first dose: -0.09 days [98.75% CI, -0.26 to 0.07], second dose: 0.06 days [98.75% CI, -0.16 to 0.29], unvaccinated notional first dose: 0.08 days [98.75% CI, -0.10 to 0.27], second dose: 0.17 days [98.75% CI, -0.04 to 0.38]). Those vaccinated during the follicular phase were also more likely to experience a clinically significant change in cycle length (8 days or more; first dose: 6.8%) than those vaccinated in the luteal phase or unvaccinated (3.3% and 5.0%, respectively; P <.001).

CONCLUSION

COVID-19 vaccine-related cycle length increases are associated with receipt of vaccination in the first half of the menstrual cycle (follicular phase).

The Multi-faceted Effects of COVID-19 on Female Reproductive Health: An Updated Narrative Review

Concerns about the SARS-CoV-2 pandemic's possible impact on sexual and reproductive health have grown significantly. In this narrative review, the latest research on the effects of SARS-CoV-2 infection on several facets of sexual and reproductive health is reviewed. The review starts initially by going through the possible consequences of SARS-CoV-2 on female menstrual cycles. The virus may interfere with the menstrual cycle, which could affect hormone synthesis and endometrial reactions, according to newly available evidence. Menstrual blood loss may be impacted by COVID-19's potential to influence endothelial cell function and systemic hemostasis. Hypothalamic amenorrhea may be brought on by severe COVID-19 disease. There is little research on this subject, although most women resume their regular menstrual cycles after 1-2 months of recuperation. The review also examines how SARS-CoV-2 infection may affect assisted reproductive technology (ART) treatments. There are few clinical data, although some research points to potential effects on embryo quality. Overall, ART results, however, did not materially change from the time before the epidemic. Obstetric problems are more likely when SARS-CoV-2 infection occurs during pregnancy, especially in the third trimester. Even though the maternal death rate is still low, pregnant women, especially those with comorbidities, are more likely to experience serious sickness. The review emphasizes how the COVID-19 vaccine affects menstrual cycles, showing brief, modest modifications without serious health hazards. Also included are the psychological effects of family planning choices during the pandemic. In conclusion, this narrative review offers a thorough assessment of the complicated and changing effects of SARS-CoV-2 on sexual and reproductive health. The different requirements of people and couples during and after the pandemic are highlighted, underscoring the necessity for ongoing study and specialized healthcare practices.

The Role of Biological Sex in Pre-Clinical (Mouse) mRNA Vaccine Studies

In this study, we consider the influence of biological sex-specific immune responses on the assessment of mRNA vaccines in pre-clinical murine studies. Recognising the established disparities in immune function attributed to genetic and hormonal differences between individuals of different biological sexes, we compared the mRNA expression and immune responses in mice of both biological sexes after intramuscular injection with mRNA incorporated within lipid nanoparticles. Regarding mRNA expression, no significant difference in protein (luciferase) expression at the injection site was observed between female and male mice following intramuscular administration; however, we found that female BALB/c mice exhibit significantly greater total IgG responses across the concentration range of mRNA lipid nanoparticles (LNPs) in comparison to their male counterparts. This study not only contributes to the scientific understanding of mRNA vaccine evaluation but also emphasizes the importance of considering biological sex in vaccine study designs during pre-clinical evaluation in murine studies.

COVID-19 and abnormal uterine bleeding: potential associations and mechanisms

The impact of COVID-19 on menstruation has received a high level of public and media interest. Despite this, uncertainty exists about the advice that women and people who menstruate should receive in relation to the expected impact of SARS-CoV-2 infection, long COVID or COVID-19 vaccination on menstruation. Furthermore, the mechanisms leading to these reported menstrual changes are poorly understood. This review evaluates the published literature on COVID-19 and its impact on menstrual bleeding, discussing the strengths and limitations of these studies. We present evidence consistent with SARS-CoV-2 infection and long COVID having an association with changes in menstrual bleeding parameters and that the impact of COVID vaccination on menstruation appears less significant. An overview of menstrual physiology and known causes of abnormal uterine bleeding (AUB) is provided before discussing potential mechanisms which may underpin the menstrual disturbance reported with COVID-19, highlighting areas for future scientific study. Finally, consideration is given to the effect that menstruation may have on COVID-19, including the impact of the ovarian sex hormones on acute COVID-19 severity and susceptibility and reported variation in long COVID symptoms across the menstrual cycle. Understanding the current evidence and addressing gaps in our knowledge in this area are essential to inform public health policy, direct the treatment of menstrual disturbance and facilitate development of new therapies, which may reduce the severity of COVID-19 and improve quality of life for those experiencing long COVID.

Messenger RNA Therapy for Female Reproductive Health

Female reproductive health has traditionally been an underrepresented area of research in the drug delivery sciences. This disparity is also seen in the emerging field of mRNA therapeutics, a class of medicines that promises to treat and prevent disease by upregulating protein expression in the body. Here, we review advances in mRNA therapies through the lens of improving female reproductive health. Specifically, we begin our review by discussing the fundamental structure and biochemical modifications associated with mRNA-based drugs. Then, we discuss various packaging technologies, including lipid nanoparticles, that can be utilized to protect and transport mRNA drugs to target cells in the body. Last, we conclude our review by discussing the usage of mRNA therapy for addressing pregnancy-related health and vaccination against sexually transmitted diseases in women. Of note, we also highlight relevant clinical trials using mRNA for female reproductive health while also providing their corresponding National Clinical Trial identifiers. In undertaking this review, our aim is to provide a fundamental background understanding of mRNA therapy and its usage to specifically address female health issues with an overarching goal of providing information toward addressing gender disparity in certain aspects of health research.

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.

Associations Among Menstrual Cycle Length, Coronavirus Disease 2019 (COVID-19), and Vaccination

OBJECTIVE

To assess whether coronavirus disease 2019 (COVID-19) is associated with menstrual cycle length changes and, if so, how that compares with those undergoing vaccination or no event (control).

METHODS

We conducted a retrospective cohort analysis in which we analyzed prospectively tracked cycle-length data from users of a period tracker application who also responded to a survey regarding COVID-19 symptoms and vaccination. We restricted our sample to users aged 16-45 years, with normal cycle lengths (24-38 days) and regular tracking behavior during the five cycles around COVID-19 symptoms or vaccination or a similar time period for those experiencing no event (control group). We calculated the within-user change in cycle length (days) from the three consecutive cycles preevent average (either vaccination, disease, or neither; cycles 1-3) to the event (cycle 4) and postevent (cycle 5) cycles. We used mixed-effects models to estimate the age- and country-adjusted difference in change in cycle length across the groups.

RESULTS

We included 6,514 users from 110 countries representing 32,570 cycles (COVID-19 symptoms: 1,450; COVID-19 vaccination: 4,643; control: 421). The COVID-19 cohort experienced a 1.45-day adjusted increase in cycle length during cycle 4 (COVID-19) compared with their three preevent cycles (95% CI 0.86-2.04). The vaccinated group experienced a 1.14-day adjusted increase in cycle length during cycle 4 (COVID-19 vaccine) compared with their preevent average (95% CI 0.60-1.69). The control group (neither vaccine nor disease) experienced a 0.68-day decrease (95% CI -1.18 to -0.19) in a similar time period. Post hoc tests showed no significant differences in the magnitude of changes between the COVID-19 and vaccination cohorts. In both cohorts, cycle length changes disappeared in the postevent cycle.

CONCLUSION

Experiencing COVID-19 is associated with a small change in cycle length similar to COVID-19 vaccination. These changes resolve quickly within the next cycle.

Influence of COVID-19 infection/vaccination on menstrual regularity and hormonal function in Saudi females of reproductive age

The COVID-19 pandemic has had a profound impact on women's health, particularly on their menstrual cycles. The menstrual cycle serves as a crucial indicator of fertility and reproduction.

Objectives

This study aimed to examine the impact of COVID-19 infection and vaccination on menstrual regularity in Saudi women of childbearing age. Additionally, it sought to explore the potential effects of COVID-19 vaccination on serum hormonal levels during the follicular phase of the menstrual cycle, along with their relationship with Vit.D.

Methods

This case‒control study investigated the impact of COVID-19 infection and vaccination on menstrual regularity and hormonal function in Saudi women of reproductive age. Data were collected from 79 women who attended the Outpatient Department of Obstetrics and Gynaecology at King Faisal Medical Complex in Taif, Saudi Arabia. All participants had received COVID-19 vaccines. The data collection process was comprehensive, encompassing various participant characteristics, such as demographic information, history of COVID-19 infection, and details about menstrual patterns before and after infection and vaccination. Furthermore, hormonal measurements, including follicle-stimulating hormone (FSH), luteinizing hormone (LH), oestradiol, prolactin, thyroid-stimulating hormone (TSH), and vitamin D (Vit.D) levels, were extracted from the participants' medical records.

Results

Among the participants, 39.24 % had a history of COVID-19 infection, and following the infection, there was a significant increase in the proportion of women experiencing irregular menstruation. After receiving the COVID-19 vaccine, 72.15 % of the participants continued to have irregular menstrual cycles. The study found that a considerable number of participants had menstrual cycles outside the normal range, with 43.80 % having cycles shorter than 21 days and 35.10 % having cycles longer than 35 days. Comparing participants with regular and irregular cycles after COVID-19 vaccination, no significant changes were observed in most hormonal levels. However, the prolactin hormone showed a significant increase in participants with irregular cycles, while Vit.D levels were significantly decreased in this group.

Conclusion

The study findings indicate a higher prevalence of irregular menstruation among participants, particularly after vaccination. Notably, irregular menstrual cycles were found to be associated with elevated levels of prolactin hormone and decreased levels of Vit.D.

Impact of COVID-19 Vaccinations on Menstrual Bleeding

INTRODUCTION

Vaccination has a fundamental role in protecting against and modifying the severity of several infectious diseases, including COVID-19. Several immune and non-immune adverse events have been reported post-COVID-19 vaccine. The aim of this study was to assess the effect of the COVID-19 vaccine on women's menstrual bleeding.

METHODS

A cross-sectional study was conducted among 399 vaccinated women in the Eastern Province of Saudi Arabia. Data were collected using a direct interview-based questionnaire including four sections.

RESULTS

A total of 399 women were recruited, with a mean age of 25.54 ± 6.177 years. More than half (53.9%) of the participants reported post-vaccination menstrual bleeding abnormality in terms of a heavy or irregular cycle. Out of the total number, 40 (21.4%) women reported having heavy menstrual flow, and 67 (16.8%) had non-menstrual bleeding after receiving the COVID-19 vaccine. Fully vaccinated women were at a greater risk of post-vaccination menstrual bleeding abnormality (p = 0.058). However, there was no correlation between booster shot type and menstrual bleeding abnormality (p > 0.05). In addition, there was no significant association between non-menstrual bleeding and the type of booster shot, the type of the first dose, and prior history of COVID-19 infection (p > 0.05).

CONCLUSION

Despite vaccination being the most effective way to prevent COVID-19, it does have an impact on menstrual bleeding in terms of menorrhagia and metrorrhagia. Therefore, more studies are needed to understand the mechanism and the long-term impact of COVID-19 vaccines on the hemostatic system.

Menstrual abnormalities after COVID-19 vaccination in the Netherlands: A description of spontaneous and longitudinal patient-reported data

AIMS

During the COVID-19 vaccination campaigns, the number of reports of menstrual abnormalities increased rapidly. Here, we describe the nature and potential risk factors associated with menstrual abnormalities based on spontaneously reporting data as well as data from a prospective cohort event monitoring (CEM) study as these are poorly studied.

METHODS

Reports of menstrual abnormalities received by the Netherlands Pharmacovigilance Centre Lareb in the spontaneous reporting system between February 2021 and April 2022 were summarized. In addition, logistic regression analysis was performed on the reported menstrual abnormalities in the CEM study to assess the association between person characteristics, prior SARS-CoV-2 infection and use of hormonal contraceptives and the occurrence of menstrual abnormalities after vaccination.

RESULTS

We analysed over 24 000 spontaneous reports of menstrual abnormalities and over 500 episodes (among 16 929 included women) of menstrual abnormalities in the CEM study. The CEM study showed an incidence of 41.4 per 1000 women aged ≤54 years. Amenorrhoea/oligomenorrhoea and heavy menstrual bleeding collectively accounted for about half of all abnormalities reported. Significant associations were observed for the age group 25-34 years (odds ratio 2.18; 95% confidence interval 1.45-3.41) and the Pfizer vaccine (odds ratio 3.04; 95% confidence interval 2.36-3.93). No association was observed for body mass index and presence of most comorbidities assessed.

CONCLUSION

The cohort study showed a high incidence of menstrual disorders among women aged ≤54 years, and this observation was supported by the analysis of spontaneous reports. This suggests that a relation between COVID-19 vaccination and menstrual abnormalities is plausible and should be further investigated.

Prevalence of and risk factors for self-reported menstrual changes following COVID-19 vaccination: a Danish cohort study

STUDY QUESTION

Are there some characteristics that render individuals more susceptible to report menstrual changes following the Coronavirus disease 2019 (COVID-19) vaccination?

SUMMARY ANSWER

We found that 30% of menstruating women reported menstrual changes following COVID-19 vaccination and several potential risk factors including stress, vaccine concerns, severe COVID-19 infection, and immediate vaccine symptoms were associated with these reports.

WHAT IS KNOWN ALREADY

Studies suggest that COVID-19 vaccination might temporarily prolong menstrual cycle length by less than 1 day. Specific characteristics may trigger menstrual changes in temporal relation to the vaccination simply by chance or render women more vigilant to potential menstrual changes after being vaccinated. However, research investigating potential risk factors for reporting menstrual changes following COVID-19 vaccination is limited.

STUDY DESIGN, SIZE, DURATION

A population-based Danish cohort study. Data were collected from May 2021 to December 2021 as a part of the BiCoVac Cohort with the aim of examining non-specific effects following COVID-19 vaccination. The main study population included 13 648 menstruating women aged 16-65 years who completed all surveys, received their first dose of a COVID-19 vaccine during the data collection period, and completed questions related to their menstrual cycle.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Potential risk factors included 14 biological, physical, or psychological measures. Information on most potential risk factors was self-reported and collected before the participants' first COVID-19 vaccination. Information about any menstrual change following COVID-19 vaccination was self-reported at the end of the data collection period. Logistic regression analyses were used to estimate crude and adjusted odds ratios (ORs) with 95% CIs for the association between each potential risk factor and reporting menstrual changes following COVID-19 vaccination.

MAIN RESULTS AND THE ROLE OF CHANCE

Any menstrual change following COVID-19 vaccination was reported by 30% of menstruating women. Most of the potential risk factors were associated with reports of menstrual changes following COVID-19 vaccination. In particular, higher odds were found among women who reported ≥5 immediate vaccine symptoms; OR 1.67 [1.50-1.86], had had a prior severe COVID-19 infection; OR 2.17 [1.40-3.35], had a high-stress level at baseline; OR 1.67 [1.32-2.10], or were concerned about COVID-19 vaccines prior to vaccination; OR 1.92 [1.50-2.45]. Lower odds were found among women with regular menstrual cycles using hormonal contraception; OR 0.71 [0.65-0.78].

LIMITATIONS, REASONS FOR CAUTION

We were unable to address the causal effect of COVID-19 vaccination on the reported menstrual changes, as information about menstrual changes was not available among non-vaccinated women.

WIDER IMPLICATIONS OF THE FINDINGS

The study identified several potential risk factors for reporting menstrual changes following COVID-19 vaccination. Further studies are needed to establish causal associations and the clinical impact of self-reported menstrual changes.

STUDY FUNDING/COMPETING INTEREST(S)

The BiCoVac data collection was funded by TrygFonden (id-number: 153678). No competing interests are declared.

TRIAL REGISTRATION NUMBER

N/A.

Identifying a causal link between prolactin signaling pathways and COVID-19 vaccine-induced menstrual changes

COVID-19 vaccines have been instrumental tools in the fight against SARS-CoV-2 helping to reduce disease severity and mortality. At the same time, just like any other therapeutic, COVID-19 vaccines were associated with adverse events. Women have reported menstrual cycle irregularity after receiving COVID-19 vaccines, and this led to renewed fears concerning COVID-19 vaccines and their effects on fertility. Herein we devised an informatics workflow to explore the causal drivers of menstrual cycle irregularity in response to vaccination with mRNA COVID-19 vaccine BNT162b2. Our methods relied on gene expression analysis in response to vaccination, followed by network biology analysis to derive testable hypotheses regarding the causal links between BNT162b2 and menstrual cycle irregularity. Five high-confidence transcription factors were identified as causal drivers of BNT162b2-induced menstrual irregularity, namely: IRF1, STAT1, RelA (p65 NF-kB subunit), STAT2 and IRF3. Furthermore, some biomarkers of menstrual irregularity, including TNF, IL6R, IL6ST, LIF, BIRC3, FGF2, ARHGDIB, RPS3, RHOU, MIF, were identified as topological genes and predicted as causal drivers of menstrual irregularity. Our network-based mechanism reconstruction results indicated that BNT162b2 exerted biological effects similar to those resulting from prolactin signaling. However, these effects were short-lived and didn't raise concerns about long-term infertility issues. This approach can be applied to interrogate the functional links between drugs/vaccines and other side effects.

Heavy bleeding and other menstrual disturbances in young women after COVID-19 vaccination

BACKGROUND

Many signals of menstrual disturbances as possible side effects of vaccination against COVID-19 have been reported. Our objective was to compare the risk of menstrual disturbances before and after vaccination among women aged 18-30 years in Oslo, Norway.

METHODS

We used electronic questionnaires to collect reports of menstrual disturbances from 3972 women aged 18-30 years, participating in the population-based Norwegian Young Adult Cohort. We examined the occurrence of menstrual disturbances (heavier bleeding than usual, prolonged bleeding, shorter interval between menstruations, longer interval between menstruations, spot bleedings, stronger pain during menstruation, period pain without bleeding) before and after the first and second dose of COVID-19 vaccine. Relative risks (RR) according to vaccination were estimated using a self-controlled case-series design. We performed additional analyses stratified by vaccine brand, contraception/hormone use, and presence of gynecological condition(s).

RESULTS

The prevalence of any menstrual disturbance was 36.7 % in the last menstrual cycle prior the first vaccine dose. The RR for heavier bleeding than usual was 1.90 (95 % CI: 1.69-2.13) after the first vaccine dose and 1.84 (95 % CI 1.66-2.03) after the second dose. Increased risks of prolonged bleeding, shorter interval between menstruations, and stronger pain during menstruation were also observed after both doses. The RRs did not differ with vaccine brand, contraception/hormone use, or presence of gynecological condition(s) for any of the menstrual disturbances.

CONCLUSION

Menstrual disturbances were common regardless of vaccination. We found increased risk of menstrual disturbances after vaccination, particularly for heavier bleeding than usual, prolonged bleeding, shorter interval between menstruations, and stronger period pain. In the future, menstrual characteristics should be included in vaccine trials.

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.

Association between SARS-CoV-2 vaccination and healthcare contacts for menstrual disturbance and bleeding in women before and after menopause: nationwide, register based cohort study

OBJECTIVES

To evaluate the risks of any menstrual disturbance and bleeding following SARS-CoV-2 vaccination in women who are premenopausal or postmenopausal.

DESIGN

A nationwide, register based cohort study.

SETTING

All inpatient and specialised outpatient care in Sweden from 27 December 2020 to 28 February 2022. A subset covering primary care for 40% of the Swedish female population was also included.

PARTICIPANTS

2 946 448 Swedish women aged 12-74 years were included. Pregnant women, women living in nursing homes, and women with history of any menstruation or bleeding disorders, breast cancer, cancer of female genital organs, or who underwent a hysterectomy between 1 January 2015 and 26 December 2020 were excluded.

INTERVENTIONS

SARS-CoV-2 vaccination, by vaccine product (BNT162b2, mRNA-1273, or ChAdOx1 nCoV-19 (AZD1222)) and dose (unvaccinated and first, second, and third dose) over two time windows (one to seven days, considered the control period, and 8-90 days).

MAIN OUTCOME MEASURES

Healthcare contact (admission to hospital or visit) for menstrual disturbance or bleeding before or after menopause (diagnosed with the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision codes N91, N92, N93, N95).

RESULTS

2 580 007 (87.6%) of 2 946 448 women received at least one SARS-CoV-2 vaccination and 1 652 472 (64.0%) 2 580 007 of vaccinated women received three doses before the end of follow-up. The highest risks for bleeding in women who were postmenopausal were observed after the third dose, in the one to seven days risk window (hazard ratio 1.28 (95% confidence interval 1.01 to 1.62)) and in the 8-90 days risk window (1.25 (1.04 to 1.50)). The impact of adjustment for covariates was modest. Risk of postmenopausal bleeding suggested a 23-33% increased risk after 8-90 days with BNT162b2 and mRNA-1273 after the third dose, but the association with ChAdOx1 nCoV-19 was less clear. For menstrual disturbance or bleeding in women who were premenopausal, adjustment for covariates almost completely removed the weak associations noted in the crude analyses.

CONCLUSIONS

Weak and inconsistent associations were observed between SARS-CoV-2 vaccination and healthcare contacts for bleeding in women who are postmenopausal, and even less evidence was recorded of an association for menstrual disturbance or bleeding in women who were premenopausal. These findings do not provide substantial support for a causal association between SARS-CoV-2 vaccination and healthcare contacts related to menstrual or bleeding disorders.

Adverse Hematological Effects of COVID-19 Vaccination and Pathomechanisms of Low Acquired Immunity in Patients with Hematological Malignancies

The SARS-CoV-2 virus and the COVID-19 pandemic have spread across the world and severely impacted patients living with hematological conditions. Immunocompromised patients experience rapidly progressing symptoms following COVID-19 infection and are at high risk of death. In efforts to protect the vulnerable population, vaccination efforts have increased exponentially in the past 2 years. Although COVID-19 vaccination is safe and effective, mild to moderate side effects such as headache, fatigue, and soreness at the injection site have been reported. In addition, there are reports of rare side effects, including anaphylaxis, thrombosis with thrombocytopenia syndrome, Guillain-Barré Syndrome, myocarditis, and pericarditis after vaccination. Further, hematological abnormalities and a very low and transient response in patients with hematological conditions after vaccination raise concerns. The objective of this review is to first briefly discuss the hematological adverse effects associated with COVID-19 infection in general populations followed by critically analyzing the side effects and pathomechanisms of COVID-19 vaccination in immunocompromised patients with hematological and solid malignancies. We reviewed the published literature, with a focus on hematological abnormalities associated with COVID-19 infection followed by the hematological side effects of COVID-19 vaccination, and the mechanisms by which complications can occur. We extend this discussion to include the viability of vaccination efforts within immune-compromised patients. The primary aim is to provide clinicians with critical hematologic information on COVID-19 vaccination so that they can make informed decisions on how to protect their at-risk patients. The secondary goal is to clarify the adverse hematological effects associated with infection and vaccination within the general population to support continued vaccination within this group. There is a clear need to protect patients with hematological conditions from infection and modulate vaccine programs and procedures for these patients.

Vaccine hesitancy: current and future challenges

Vaccine hesitancy, defined by the WHO as reluctance or refusal to vaccinate, despite the availability of vaccines, threatens to undermine progress in tackling vaccine-preventable disease. In this Immunology Futures article, I explore my experiences of combating vaccine hesitancy, and how research in this area can help. The graphic was made with assets from Freepik.com.

Association between COVID-19 vaccines and the menstrual cycle in young Japanese women

INTRODUCTION

Although several studies have investigated the association between coronavirus disease 2019 (COVID-19) vaccines and the menstrual cycle, available data are limited. Therefore, this study investigated the effect of COVID-19 vaccines on the menstrual cycle and the effect of the menstrual cycle phase on the vaccine side effects during vaccine administration in Japan.

METHODS

A self-administered questionnaire was used to collect data on the date of vaccination; type of vaccine; type, grade, and duration of the side effects; regularity of menstruation; normal length of the menstrual cycle; and the day one date of menstruation around vaccination. The survey was conducted from October 2021 to March 2022.

RESULTS

The difference between the predicted and actual menstrual cycle length was 1.9 ± 3.0, 1.6 ± 2.8 (p = 0.557), and 2.5 ± 3.8 (p = 0.219) days before vaccination and after the first and second dose of the vaccine, respectively. In participants who received vaccinations twice within a single menstrual cycle, this difference was 1.3 ± 3.5 and 3.9 ± 3.3 (p = 0.045) days before and after vaccination, respectively. The grade and proportion of the side effects after the second dose of the vaccine was highest during the menstrual period and lowest during the ovulation period, with a significant effect on headache and chills.

CONCLUSION

COVID-19 vaccines tended to prolong the menstrual cycle. The side effects of the COVID-19 vaccine tended to be at a maximum when vaccination occurred during the menstrual period and minimal during the ovulation period.

COVID-19 vaccination and menstruation

COVID-19 vaccination causes small changes to menstruation that quickly resolve

Covid-19 vaccination and menstrual cycle length in the Apple Women's Health Study

COVID-19 vaccination may be associated with change in menstrual cycle length following vaccination. We estimated covariate-adjusted differences in mean cycle length (MCL), measured in days, between pre-vaccination cycles, vaccination cycles, and post-vaccination cycles within vaccinated participants who met eligibility criteria in the Apple Women's Health Study, a longitudinal mobile-application-based cohort of people in the U.S. with manually logged menstrual cycles. A total of 9652 participants (8486 vaccinated; 1166 unvaccinated) contributed 128,094 cycles (median = 10 cycles per participant; inter-quartile range: 4-22). Fifty-five percent of vaccinated participants received Pfizer-BioNTech's mRNA vaccine, 37% received Moderna's mRNA vaccine, and 8% received the Johnson & Johnson/Janssen (J&J) vaccine. COVID-19 vaccination was associated with a small increase in MCL for cycles in which participants received the first dose (0.50 days, 95% CI: 0.22, 0.78) and cycles in which participants received the second dose (0.39 days, 95% CI: 0.11, 0.67) of mRNA vaccines compared with pre-vaccination cycles. Cycles in which the single dose of J&J was administered were, on average, 1.26 days longer (95% CI: 0.45, 2.07) than pre-vaccination cycles. Post-vaccination cycles returned to average pre-vaccination length. Estimated follicular phase vaccination was associated with increased MCL in cycles in which participants received the first dose (0.97 days, 95% CI: 0.53, 1.42) or the second dose (1.43 days, 95% CI: 1.06, 1.80) of mRNA vaccines or the J&J dose (2.27 days, 95% CI: 1.04, 3.50), compared with pre-vaccination cycles. Menstrual cycle change following COVID-19 vaccination appears small and temporary and should not discourage individuals from becoming vaccinated.

Effect of COVID-19 vaccination on the menstrual cycle

Numerous anecdotal accounts and qualitative research studies have reported on post-vaccination menstrual irregularities in women of reproductive age. However, none have quantified the impact. This is the first systematic review and meta-analysis to quantify and characterize the menstrual irregularities associated with vaccination for women of reproductive age. A search on July 20, 2022, retrieved articles published between December 1, 2019, and July 1, 2022, from MEDLINE, Embase, and Web of Science. The included articles were studies with full texts written in English that reported on menstrual irregularities for vaccinated vs. unvaccinated women of reproductive age. The quality of the studies was evaluated using the Study Quality Assessment Tool for Observation Cohort and Cross-Sectional Studies. Four observational studies were included. Review Manager was used to generating a forest plot with odds ratios (ORs) at the 95% confidence interval (CI), finding statistically significant associations between vaccination and menstrual irregularities for 25,054 women of reproductive age (OR = 1.91, CI: 1.76-2.07) with a significant overall effect of the mean (Z = 16.01, p < 0.0001). The studies were heterogeneous with significant dispersion of values (χ² = 195.10 at df = 3, p < 0.00001, I ² = 98%). The findings of this systematic review and meta-analysis are limited by the availability of quantitative data. The results have implications for treating women of reproductive age with menstrual irregularities and informing them about the potential side effects of vaccinations.