42% of women report menstrual changes after COVID vaccine

A report from Science Advances explores the effects that the COVID-19 vaccine has had on 40,000 women, with 42% reporting changes to their menstrual cycle

A recent report found that 42% of respondents had heavier cycles after receiving the COVID-19 vaccine, according to Science Advances.

Through the study, researchers argued that although vaccine manufacturers have not studied how women’s menstrual cycles are affected by the COVID vaccination, “many people” have claimed that they have “experienced unexpected menstrual bleeding”. 

The research included respondents that had received vaccines from a variety of different manufacturers, yet mainly including Pfizer vaccine (21,620) or Moderna (13,001). Smaller samples of respondents received Johnson & Johnson, Novavax, and “other” vaccines. 

As a result of this, the researchers used self-reported data from a sample of almost 40,000 females across various demographics and sub-demographics, to explore how women’s menstrual cycles have been affected and the symptoms they received.

How has the COVID-19 vaccine affected women’s periods? 

The study found that 42% of women experienced heavier bleeds than before the COVID-19 vaccine, and 44% reported no changes. In addition, the data found that a high number of non-menstruating women reported breakthrough bleeding, most of which occurred within a week of receiving their first and second doses.

Study author Dr Kathryn Clancy completed the research with her colleague, Dr Katharine Lee. Dr Kathryn said: “If Dr. Lee hadn’t pointed them [the symptoms] out to me first, I may never have made the connection myself. 

“After I tweeted about it and the response was overwhelming, we designed a survey instrument that would allow us to capture these experiences as well as any factors that might make one more at risk of this side effect. We really wanted to listen to people and validate their concerns because there were so many who were quick to dismiss them.”

“Our key finding is that increased bleeding (heavier among menstruating people, and breakthrough bleeding among non-menstruating people) is real, mechanistically plausible and experienced by a significant number of people. It is also now supported by several prospective studies that have also found the same thing.”

How will this affect women in the workplace?

Insurance company Bupa found that women who receive heavy periods and painful cramps are more likely to feel unwell and less productive at work. A survey of 2,000 women revealed that 23% of women have taken time off work because of their period in the last 6 months –  36% not telling the truth about why they were unable to work, saying they either have a stomach bug or the flu. Women under the age of 25 were more likely to use these reasons, with 58% giving the excuse of a stomach bug or flu.

On behalf of Bupa, Dr Petra Simic states: “If you’re in work and experiencing any uncomfortable symptoms, you should try to continue with your day as much as possible. Knowing how to minimise your discomfort is important, so make sure you’ve got some appropriate pain relief. Taking this, along with drinking plenty of water and getting as much rest as you can will help. If you’re feeling irritated or anxious, try to be open and honest with your colleagues.”


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