Effect of COVID-19 vaccination on menstrual periods in a retrospectively recruited cohort

Surveillance schemes are receiving increasing numbers of reports from people who have noticed a change to their period following COVID-19 vaccination. In order to investigate this, we retrospectively recruited 1273 people who have a record of their menstrual cycle and vaccination dates and used their reports to explore hypotheses about how COVID-19 vaccination and menstrual changes could be linked. In this dataset, we were unable to detect strong signals to support the idea that COVID-19 vaccination is linked to menstrual changes. However, larger, prospectively recruited studies may be able to find associations that we were not powered to detect.