Effect of COVID-19 Vaccination on Menstrual Cycle Patterns of Reproductive-age Women: A Multi-centric Observational Study.

Aim: The study was conducted to know the impact of COVID-19 vaccination on menstrual cycle patterns and pre- and post-menstrual symptoms in women aged 18-45 years.

Background: COVID-19 vaccination was introduced to combat the dreadful impacts of human coronavirus infection. The two indigenously developed COVID-19 vaccines approved for use in India are COVISHIELD and COVAXIN.

Objectives: To investigate the effects of COVID-19 vaccination on the menstrual cycle, pre- and post-menstrual symptoms and to establish the correlation with the type of vaccine received.

Methods: Multi-centric observational study conducted in six institutes of national importance in different states of India over one year. A total of 5709 female participants fulfilling inclusion criteria were enrolled. Data about the impact of vaccines (COVISHIELD and COVAXIN) and prior COVID-19 infection on the menstrual cycle and its associated symptoms were obtained using all participants' online and offline interviews.

Results: Of 5709 participants, 78.2% received COVISHIELD and 21.8% COVAXIN. Of the total 5709 participants, 333 (5.8%) developed post-vaccination menstrual disturbances, with 32.7% having frequent cycles, 63.7% prolonged cycles, and 3.6% inter-menstrual bleeding. A total of 301 participants noticed changes in the amount of bleeding, with 50.2% excessive, 48.8% scanty, and 0.99% amenorrhea followed by heavy bleeding. Furthermore, the irregularities of the menstrual cycle (p = 0.011) and length (0.001) were significantly higher in the COVAXIN group (7.2%) as compared to the COVISHIELD (5.3%) group. A total of 721 participants complained of newly developed/worsening pre- and post-menstrual symptoms. These symptoms were significantly higher in the COVISHIELD group (p = 0.031), with generalized weakness and body pains as the main complaints (p = 0.001). No significant difference was observed in the incidence of COVID-19 infection with these vaccines. No significant associations were observed when comparing menstrual abnormalities among those with COVID-19 infection (p > 0.05).

Conclusion: COVISHIELD and COVAXIN vaccines were associated with menstrual cycle disturbances and pre-and post-menstrual symptoms in a small proportion of participants, with 94.7% having no change in the amount of bleeding during menstruation post-vaccination. The menstrual irregularities observed were significantly higher with the COVAXIN vaccine. Others: Further, long-term studies are required to confirm that the impact of COVID-19 vaccination on the menstrual cycle may be short-lasting, with no severe effects on women's menstrual health.