A new pre-print study suggests another way in which the vast chemical reaction that is the human body is impacted by vaccinations against the coronavirus.
The study links the vaccines to changes in the menstrual cycles of women taking contraceptives.
The study, published on MedRxiv.org, noted that menstrual changes are more significant in women who are taking contraceptives.
The study, which was done in Britain, was triggered by an increase in reports to Britain health service that the vaccine had impacted menstrual periods.
The study consisted of 1,273 British women responding to questionnaires about their vaccinations and subsequent menstrual periods. The study covered women who had the Pfizer-BioNTech, Moderna and AstraZeneca vaccines.
The report said researchers “were unable to detect strong signals to support the idea that COVID19 vaccination is linked to menstrual changes,” but that larger studies might be able to do so.
A total of 2,241 women were recruited for the study, but some results were “cleaned” from the data set for various reasons, including becoming pregnant the same month as being vaccinated.
Results showed that among those on hormonal contraception, 42 percent said their periods were heavier than usual, and 19 percent found they were lighter. Of those not taking birth control, 32 percent said their periods were heavier and 14 percent said they were lighter.
The study reported that 57 percent of women on contraceptives had their menstrual period either earlier or later than usual after being vaccinated. That was two percentage points higher than the response from women who were not on contraceptives.
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Dr. Victoria Male, the Imperial College London immunologist who led the study, said it was “difficult” to suggest a biological reason for the results, according to the Daily Mail.
“A lot of people who take hormonal contraception at least partially want to control their periods,” she said.
“It could be that they are more likely to report the change because the contraception normally makes their periods very regular — so it’s particularly unusual for them,” she said.
She also suggested that women taking contraceptives may monitor their periods more closely, which would impact the responses to the study.
The study indicated that changes reported do not appear to last more than a month beyond being vaccinated.
“Most women don’t seem to be seeing an effect and most who are potentially vulnerable should still get the jab because, in the short term, we know that getting a Covid infection also affects periods,” she said.
Male noted that although the study did not address concerns about infertility and the vaccines, “In this study, some 36 women became pregnant from the 2,000 involved, so that’s quite a lot.”
British authorities have received more than 41,000 reports of menstrual changes after being vaccinated against the coronavirus.
The study noted that its limitations included the relatively small size of the sample and the fact that all those surveyed were from Britain.