Association between Covishield vaccine and menstrual disturbance. Findings from a cross-sectional study among participants of Zero TB cohort in India

Background: The association between covid-19 vaccine and menstrual disturbance is unclear. Methods: An in-person cross-sectional survey among female members ≥ 18 years enrolled in an ongoing Zero TB prospective cohort in Northern India who had received one or two doses of covid-19 vaccine was conducted to study the characteristics and association of menstrual disturbance within six months of receiving Covishield. Results: Between June 29 and September 5, 2021, 339 females ≥ 18 years of age were administered the survey. Median age was 30 (IQR: 22–39) years; 84 % were between 18 and 49 and 16 % were ≥ 50 years old. There were 152 college students, 27 healthcare workers, and 160 nuns. Forty-two women (12 %) had received one dose and 297 (88 %) had received two doses of Covishield. Overall, 66 (20 %) women reported experiencing menstrual disturbance after receiving Covishield vaccine. The problems included early menstruation: 6 % (n = 19/339); late menstruation: 4 % (n = 14/339); and heavier bleeding: 5 % (n = 17/339). Disturbances lasted for less than seven days and cycles normalized in 1–3 months. There was no post-menopausal bleeding. There was no significant difference in menstrual disturbance based on receiving one vs. two doses of Covishield (OR: 1.58; 95 % CI: 0.55–4.57; p = 0.381). History of SARS-CoV-2 infection was not associated with the development of menstrual disturbance among the vaccinees (OR: 0.63; 95 % CI: 0.24–1.73; p = 0.379). Presence of emotional disturbance at baseline (OR: 31; 95 % CI: 3.52–267; p = 0.002) or previous history of dysmenorrhea (OR: 41; 95 % CI: 8.7–196; p < 0.001) was associated with menstrual disturbance in the vaccinees, indicating their potential to confound or bias study results. Conclusion: Menstrual problems were reported by Covishield vaccinees, but they were minor and reversible within three months and do not constitute a ground for vaccine hesitancy. Studies designed to assess causal link taking care to avoid selection bias or confounding are needed.