COVID-19 Vaccination May Momentarily Interfere With Menstruation

Oct, 2022 - By WMR

Some women noticed changes in the timing and duration of their menstrual periods after receiving the COVID-19 vaccination when it first became widely accessible.

Nearly two years later, a worldwide investigation has verified that for certain individuals, COVID-19 immunisation can cause transitory alterations in cycle duration.

An FDA-approved birth control app called Natural Cycles was used by over 20,000 women from all over the world to self-report their menstrual cycles for the study, which was then published in the medical journal BMJ.

Participants in the trial who got the injection reported an average lengthening of their menstrual cycle of about one day after receiving the first dose of the COVID vaccine, and of about half a day after receiving the second dose.

The duration of the menstrual cycle increased by almost four days in those who got both vaccination doses in a single period.

The study concluded that variations in cycle length are merely transient and have no long-term impacts, which is in line with other studies' findings.

A smaller research conducted earlier this year involving around 4,000 women had similar findings, noting that a regular menstrual cycle resumed one to two months following vaccination.

The tenacity of the women who spoke out on social media and shared details of their adverse effects in an online database set up by two academics allowed the two studies to get off the ground.

A few months later, in August 2021, the National Institutes of Health said it will allocate $1.6 million in funding to five colleges around the US to begin research on the topic.

"On a human level, any apparent change to a person's cycle — whether it be due to vaccination or other external pressures — can really appear big," says Edelman, the lead author of the two studies that have been published thus far.