GP consultations for menstrual disorders after COVID-19 vaccination – a self-controlled cohort study based on routine healthcare data from the Netherlands

Background: Several studies described that COVID-19 vaccinations can cause menstrual disorders. Our study aimed to describe whether this also resulted in more general practitioner (GP) consultations for menstrual disorders after COVID-19 vaccination.

Objectives: The primary aim is to analyse whether there is an increase in GP consultations for menstrual disorders after COVID-19 vaccinations. Secondary aims are to determine risk factors and risk groups with increased GP consultations for menstrual disorders after COVID-19 vaccinations.

Methods: A self-controlled cohort study was performed including vaccinated women aged 12-49 years from two large, representative GP databases in the Netherlands (i.e. Nivel Primary Care Database and PHARMO GP database). Women were excluded if they consulted the GP for a menstrual disorder in the six months before January 1, 2021 (cohort entry date), if no data was available in the six months before cohort entry, or if they had been diagnosed with postmenopausal bleeding. All included women were followed from cohort entry date until the GP was consulted for a menstrual disorder in 2021, until deregistration at the GP practice in 2021, or until December 31, 2021 was reached, whichever cohort exit date came first. The follow-up period is defined as the time between the cohort entry date and cohort exit date. The exposed period was set at maximum six months after each COVID-19 vaccination and the non-exposed period was defined as the follow-up period minus the exposed period. Incidence rates and incidence rate ratio’s (IRR) were calculated using Poisson regression, adjusting for SARS-CoV-2 infection as time-varying confounder. P-values < 0.05 were considered statistically significant.

Results: The cohort included 631.802 women, of which 18.986 (3%) consulted the GP for a menstrual disorder. Increased GP consultations were observed among 12-14-year olds for amenorrhea/hypomenorrhea/oligomenorrhea (IRR: 1.87, 95% CI: 1.31-2.67) and irregular/frequent menstruation (IRR: 1.35, 95% CI: 1.06-1.70) after Pfizer/BioNTech vaccination. Persons from this age group were in general also vaccinated with the Pfizer/BioNTech vaccine. No increase in the frequency of GP consultations were observed for older age groups, other vaccine brands, and potential risk groups.

Conclusions: For the majority of women, no increased GP consultations for menstrual disorders was found. Solely for the youngest age group an increase in GP consultations for specific types of menstrual disorders was found. It is possible that older age groups perceive menstrual disorders as less serious and therefore did not actively seek medical help.