Covid-19 vaccination tied with temporary change in menstrual cycle length: study

A study was conducted to identify whether covid-19 vaccines are associated with menstrual changes in order to address concerns about menstrual cycle disruptions after covid-19 vaccination.

Participants 19 622 individuals aged 18-45 years with cycle lengths of 24-38 days and consecutive data for at least three cycles before and one cycle after covid (vaccinated group; n=14 936), and those with at least four consecutive cycles over a similar time period (unvaccinated group; n=4686). The mean change within individuals was assessed by the vaccination group for cycle and menses length (mean of three cycles before vaccination to the cycles after the first and second dose of vaccine and the subsequent cycle). Mixed effects models were used to estimate the adjusted difference in change in cycle and menses length between the vaccinated and unvaccinated.

Results:

• Most people (n=15 713; 80.08%) were younger than 35 years, from the UK (n=6222; 31.71%), US and Canada (28.59%), or Europe (33.55%).
• Two thirds (9929 (66.48%) of 14 936) of the vaccinated cohort received the Pfizer-BioNTech (BNT162b2) covid-19 vaccine, 17.46% (n=2608) received Moderna (mRNA-1273), 9.06% (n=1353) received Oxford-AstraZeneca and 1.89% (n=283) received Johnson & Johnson
• Individuals who were vaccinated had a less than one day adjusted increase in the length of their first and second vaccine cycles, compared with individuals who were not vaccinated
• The adjusted difference was larger in people who received two doses in a cycle (3.70 days increase
• One cycle after vaccination, cycle length was similar to before the vaccine in individuals who received one dose per cycle compared with unvaccinated individuals.
• Changes in cycle length did not differ by the vaccine's mechanism of action (mRNA, adenovirus vector, or inactivated virus).
• Menses length was unaffected by vaccination.

Thus, Covid-19 vaccination is associated with a small and likely to be a temporary change in menstrual cycle length but no change in menses length.

Reference:

Edelman A, Boniface ER, Male V, et al. Association between menstrual cycle length and covid-19 vaccination: a global, retrospective cohort study of prospectively collected data. BMJ Medicine 2022;1:e000297. doi: 10.1136/bmjmed-2022-000297

Keywords:

Association, between, menstrual, cycle, length, covid-19, vaccination, global, retrospective, cohort study, prospectively, collected, data, Alison Edelman, Emily R Boniface, Victoria Male, Sharon T Cameron, Eleonora Benhar, Leo Han, Kristen A