Women who got vaccinated against Covid-19 reported having slightly longer menstrual cycles, a new global study has found. The temporary increase was not impacted by the type of vaccine. This is the latest in studies examining the effects of the Covid-19 vaccines on menstrual cycles.
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Vaxxed vs unvaxxed
The study, conducted by the US National Institute of Health (NIH) studied data collected from nearly 20,000 people from across the UK, Canada, the United States, Europe and other parts of the world. The participants had all received at one of nine Covid-19 vaccines.
The study published in the journal BMJ Medicine found that the cycle length lasted for at least half a day, normalizing for most of the participants following vaccination. The researchers from universities in the US and the UK wrote:
Compared with the unvaccinated group, vaccinated individuals had an adjusted increase in menstrual cycle length of less than one day with both first and second vaccine doses.
The changes observed in the length of the cycle of individuals who received two doses in a single cycle stood at an average of 3.70 days compared with the unvaxxed participants.
Impact
The NIH gave $1.67 million to five institutions to investigate any plausible impact of Covid-10 vaccines on menstrual cycle length. In January this year, the team of researchers published initial findings establishing a link. This recent study is a confirmation of that theory.
Dr. Diana Bianchi, director of the National Institute of Health’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) said in a news release:
These findings provide additional information for counseling women on what to expect after vaccination. Changes following vaccination appear to be small, within the normal range of variation, and temporary.
A different study published in August concluded that some individuals experienced heavier bleeding after vaccination.
Sources Used:
CTV News: COVID-19 vaccines linked to temporary changes in menstrual cycle, new study confirms
CNN: Study links Covid-19 vaccination to small, temporary change in menstrual cycle
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