Discussion
The present study included 5709 participants, with 4464(78.2%) having received COVISHIELD, and 1245(21.8%) had COVAXIN against COVID-19 infection. Of the total 5709 participants, 333(5.8%) developed post-vaccination irregularities of menstruation with 32.7% having frequent cycles (every ≤20 days), 63.7% prolonged cycles (>38 days), and 3.6% inter-menstrual bleed. A total of 301 participants (5.3%), noticed changes in the amount of bleeding during menstruation, with 50.2% having excessive, 48.8% scanty bleeding, and 0.99% had amenorrhea followed by heavy bleeding. Furthermore, the irregularities of the menstrual cycle (p=0.011) and cycle length (0.001) were significantly higher in the COVAXIN group (7.2%) as compared to the COVISHIELD vaccine (5.3%). No significant difference was observed in the duration and amount of menstrual bleeding in the two vaccine groups (p>0.05). A total of 721 (12.4%) participants complained of newly developed or worsening pre- and post-menstrual symptoms. These symptoms were significantly higher in the COVISHIELD group (p=0.031).
Similar results of the impact of COVID-19 vaccination on menstrual cycles were reported by other studies from all across the world. A study conducted on 950 women to know the impact of COVID-19 vaccination on the menstrual cycle, reported changes in frequency (normal 43.47%, infrequent 25%, and frequent 31.53%), regularity (regular 51.08%, irregular 42.93%, and absent/amenorrhea 5.97%), duration (normal 65.21%, prolonged 26.08%, absent/amenorrhea 8.69%), and volume (heavy 41.84%, light 20.65%, and amenorrhea 6.52%) of menstruation in 184 women out of 408 fulfilling the inclusion criteria. It was concluded that COVID-19 vaccination can influence the menstrual cycle and cause alterations.19 A recent cross-sectional study from the Middle East and North Africa was conducted on 2269 females fully vaccinated against COVID-19 infection to assess the impact of vaccines (AstraZeneca, Sinopharm, and Pfizer) on menstrual abnormalities and reported that 66.3% of participants reported abnormal menstrual symptoms post-vaccination with the resolution of these symptoms within 2 months in 93.6% of participants. Similar to our study it was observed that vaccine type did not significantly affect the incidence of abnormalities (p > 0.05). Furthermore, they also reported that participants with confirmed previous COVID-19 infection had a similar percentage of menstrual abnormalities compared to those who did not have COVID-19 infection. Hence, it was concluded that women subjected to COVID-19 vaccines experienced menstrual abnormalities including, longer menstruation duration and increased menstrual cycle lengths.20
Another cohort study was conducted in the United States of America on 3,959 women (vaccinated 2,403; unvaccinated 1,556) to assess the association between COVID-19 vaccination (Pfizer-BioNTech, Moderna and Johnson & Johnson/Janssen vaccines) and changes in menstrual cycle length. It was observed that the COVID-19 vaccine was associated with a < 1-day change in cycle length compared to pre-vaccine cycles. Hence, it was concluded that COVID-19 vaccination was associated with only a small change in the cycle length but not the duration of menstrual bleeding.11 Another similar study was conducted on 19,622 women between 18-45 years of age to know whether the COVID-19 vaccines (Pfizer-BioNTech, Moderna, Oxford-AstraZeneca, and Johnson & Johnson) were associated with menstrual changes. It was reported that vaccinated women had a < 1-day adjusted increase in the cycle length as compared to the unvaccinated ones. Furthermore, it was observed that the adjusted difference was larger in women who received two doses. Hence, it was concluded that COVID-19 vaccination was associated with a small and temporary change in the menstrual cycle length without affecting the bleeding duration.21 A similar recent study was conducted on 9,652 women (8,486 vaccinated; 1,166 unvaccinated) to know the impact of COVID-19 vaccines on the menstrual cycle length. All the participants were followed for 10 cycles and it was found that the vaccinated women had a small increase in mean cycle length. It was concluded that COVID-19 vaccination was associated with an immediate short-term increase in menstrual cycle length.22
Very few studies have been conducted to know the impact of COVID-19 vaccination on pre-and post-menstrual symptoms. A recent questionnaire-based study compared menstruation characteristics (regularity, volume, intermenstrual bleeding, and dysmenorrhea) before and after receiving the COVID-19 vaccine in Saudi Arabia and reported a significant impact of COVID-19 vaccination on menstrual disturbances.23
In the present study a total of 721(12.6%) participants suffered from COVID-19 infection before, during, or after the completion of vaccination. Of these, 584(81.0%) participants received the COVISHIELD vaccine and the remaining 137(19.0%) had the COVAXIN vaccine (p=0.236). No significant difference was observed in the incidence of COVID-19 infection with either COVAXIN or COVISHIELD vaccines (p>0.05). When comparing menstrual abnormalities including cycle length, and amount of bleeding among those with a history of COVID-19 infection before, during, or after vaccination, no significant associations were observed (p >0.05). A similar study was conducted on 483 women from Jordan and Iraq to evaluate menstrual changes in women post-COVID-19 infection. It was reported that 47.2% of women suffered from a change in the number of days between two consecutive cycles, and a change in the amount of bleeding during menses post-infection. Hence, it was concluded that COVID-19 infection may affect the menstrual cycle pattern in females.24Similar results of menstrual cycle disturbances in women post-COVID-19 infection have been reported by other studies25-27, but still, further research is necessary for better evidence and conclusion.