A study of almost three million women has found no evidence of an increased risk of menstrual changes after receiving a Covid-19 vaccine. In a paper published in the BMJ, researchers suggested only a weak association between the vaccine and menstrual disturbance or premenstrual bleeding. The study provides no substantial support for a causal association between the Covid-19 vaccination and healthcare contacts related to menstrual or bleeding disorders.
Many women have self-reported changes to their periods after receiving a Covid-19 vaccine, including excessive, frequent, absent, or irregular menstruation. The potential link between the vaccine and menstrual disturbance has also been discussed on social media, causing global concern.
The researchers in Sweden drew on high-quality health registry data to evaluate the risks of menstrual disturbance and bleeding after the Covid-19 vaccination in 2,946,448 women aged 12-74 from December 2020 to February 2022. This study included an assessment of Pfizer-BioNTech, Moderna, and Oxford-AstraZeneca vaccines, along with the dose number (unvaccinated and first, second, and third dose).
The authors, led by Rickard Ljung, professor at the Swedish Medical Products Agency, concluded that weak and inconsistent associations existed between the SARS-CoV-2 vaccination and healthcare contacts for postmenopausal bleeding. The association was even less consistent for menstrual disturbance and premenstrual bleeding.
The healthcare contacts in the study included primary care visits, specialist outpatient visits, and days of hospital stay related to menstrual disturbance or bleeding before or after menopause. More than 88% of women received at least one Covid-19 vaccine, and over 64% of vaccinated women received three doses during the study period.
Although the analysis suggested a 23-33% increased risk of post-menopausal bleeding after eight to 90 days with Pfizer-BioNTech and Moderna after the third dose, a less clear association was observed with Oxford-AstraZeneca. However, after adjusting for socioeconomic factors, previous healthcare use, and specific medical conditions, the study concluded that these weak associations almost completely disappeared, suggesting that a casual effect is unlikely.
Meanwhile, a large study found that up to one in 20 new cases of diabetes could be linked to Covid-19 infection. An analysis of records from almost 630,000 people between the beginning of 2020 and the end of 2021 found a significantly higher rate of incident diabetes in those who had PCR-confirmed Covid-19.
In conclusion, this study provides reassurance that receiving a Covid-19 vaccine does not have a significant impact on menstrual cycles. The researchers involved in the study suggest that any observed menstrual disturbances are likely due to other factors, such as stress, anxiety, or changes in physical activity levels, rather than the vaccine itself. As vaccination remains the cornerstone of the global effort to curb the spread of Covid-19, this finding should help to encourage more women to get vaccinated without fear of menstrual disturbance side effects.
