Tit’s easiest The way to promote a conspiracy theory is to take the grain of truth and blow it out of sane proportions. This is exactly how one of the most prominent sources of covid-19 vaccine hesitancy – misinformation about its effect on women’s fertility – spread.
Your browser does not support the element
When women of reproductive age started getting the vaccine in large numbers in the (northern) summer of 2021, some people noticed that their post-vaccination periods were longer than usual. By September of that year, there were more than 30,000 reports to the British medicines regulator alone of late episodes following covid vaccines (with the true figure likely higher, due to under-reporting). Anti-vaxxers then used this phenomenon to scare women with speculation about long-term damage to their fertility.
Research just published in the BMJ by Alison Edelman of Oregon Health & Science University in Portland and her colleagues have confirmed both that the effect is real and that it may not be anything to worry about. Taking data from users of Natural Cycles, a menstrual cycle tracking app, she and her team found that covid vaccination was associated with a small but temporary increase in cycle length.
Among those who received one dose of vaccine in a menstrual cycle, periods were on average almost one day late. Those who received two doses in one cycle saw an average delay of four days. For both groups, cycle length returned to normal in the cycle after their second dose, referred to as the “post-vaccination cycle”.
Dr Edelman’s study analyzed data provided by 19,622 app users from around the world, although the majority lived in Europe or North America. A quarter of them, who were controls, were unvaccinated. The vaccinated participants had received several types of vaccination (e.gRNA, adenovirus vector or inactivated virus). The type of vaccine made no difference to the outcome.
For a participant to be included, her app had to collect three cycles of data before her vaccination as well as the cycles after the first and second doses of the vaccine, and the cycle from after the vaccination. For unvaccinated participants the requirement was four consecutive cycles.
On average, delays in vaccinated individuals were within the normal range – up to eight days. So for the most part, vaccines did not cause medical concern. However, the researchers found that 6.2% of the time participants were vaccinated immediately after receiving a dose of vaccine more than eight days late. Those experiencing these abnormally long periods in the cycle after vaccination tended to have longer cycles already. There was no evidence that this effect continued after the post-vaccination cycle, but the trial was not specifically set up to look for that, so Dr. Edelman says , “the group would like to explore that result in future research.”
The world’s covid-19 vaccine programs actually provide a golden opportunity to study how vaccines are studied. At no time before had governments across the planet attempted to vaccinate all adults (including all women of reproductive age) at the same time.
Currently, to prevent the risk of miscarriage and harm to fetuses during vaccine trials, it is standard practice for women of reproductive age participating in such trials to use control birth That is a sensible warning, as was the decision not to include pregnant women in certain formal clinical trials. (The U.S. Centers for Disease Control and Prevention instead conducted real-world trials, in which pregnant women could opt-in, along with the main vaccine rollout.) But this abundance of caution is co-opted. related to pregnancy and reducing the risk of harm to fetuses meaning that, as in this case, side effects that women of reproductive age may have on their menstrual cycles have been lost.
So vaccine manufacturers, health regulators and scientists were caught off guard when reports of late times began to emerge as vaccine distribution, which began among the elderly, who were at risk of dying if infected, declined. the demographic pyramid to women. who had not yet reached menopause. It was difficult for medical advice to keep up with the pace of misinformation because reports of late periods as side effects could not be found in clinical trials.
Without proof that this was a temporary phenomenon, false speculation and fake news found fertile ground in an often sensitive and emotional issue. Dr. Edelman’s results should go some way to contradicting that. ■
Do you know about the world? To enjoy our mind-expanding science coverage, sign up to Simply Science, our weekly newsletter.
