NIH Invests $1.67 Million to Study How Vaccines Impact the Menstrual Cycle 

WASHINGTON — The NIH recently invested $1.67 million in five institutions to explore the link between COVID-19 vaccines and menstruation changes, as some women are reporting irregular or missing menstrual periods after receiving a vaccine. 

Only a few weeks after the NIH investment was released, an editorial was published in the British Medical Journal from a researcher at the Imperial College of London who indicated that the link between menstruation changes and vaccination is plausible and should be investigated.  

“Since May, I have been running a small study on this. I recruited 250 people before they had their vaccine, and they are keeping a record of their periods before the vaccine and for a couple of months afterwards. This will give us an idea of what a normal menstrual cycle looks like for each of these people, and then we can compare the experience after the vaccine with what they were experiencing before,” said Victoria Male, Imperial College of London. 

In the UK, the Medicine and Healthcare Products Regulatory Agency monitors for adverse drug reactions, and more than 30,000 reports of changes to periods and unexpected vaginal bleeding were reported to primary care clinicians and those working in reproductive health. 

Male said that while hard evidence is not yet available, any changes in menstruation from receiving vaccination is likely the result of the immune response to vaccination rather than a specific vaccine component. 

“We have reports of​ menstrual changes following vaccination with both mRNA vaccines, Pfizer and Moderna, and Adenovirus-vectored vaccines, AstraZeneca and Janssen. These are quite different in terms of what’s in them, so that suggests that it’s not any particular ingredient that is causing the changes,” said Male.  

Male also said that most people who report a change to their period after vaccination find that it returns to normal the following cycle. 

More importantly, there is no evidence that COVID-19 vaccination adversely affects fertility, as concerns are being raised that that vaccine hesitancy among young women is largely driven by false claims that COVID-19 vaccines could harm their chances of future pregnancy.  

“The idea that the vaccines might harm female fertility came from a piece of misinformation that was first circulated in December, before the vaccines had even been rolled out,” said Male. 

Male said that in the clinical trials, and in four studies done in IVF clinics, being vaccinated makes no difference to the chance that a woman will become pregnant.  

Still, more definitive evidence is needed to understand if there is a link between vaccines and menstruation. The NIH one-year grant awarded to five institutions will continue to build on existing research and leverage data from menstrual tracking applications, with one project focused specifically on adolescents.