Menstrual changes after covid-19 vaccination

Common side effects of covid-19 vaccination listed by the Medicines and Health Products Regulatory Agency (MHRA) in the UK include arm pain, fever, fatigue and myalgia. 1 Period changes and unexpected vaginal bleeding are not listed, but primary care clinicians and those working in reproductive health are increasingly approached by people who have experienced these events soon after. the vaccination. More than 30,000 reports of these events had been submitted to the MHRA yellow card surveillance program for adverse drug reactions as of September 2, 2021, for all currently available covid-19 vaccines.1

Most people who report a change in their period after vaccination find that they return to normal by the next cycle and, most importantly, there is no evidence that vaccination against covid-19 negatively affects fertility. In clinical trials, unintended pregnancies have occurred at similar rates in the vaccinated and unvaccinated groups.2 In assisted reproduction clinics, fertility measurements and pregnancy rates are similar in vaccinated and unvaccinated patients. 3456

MHRA says assessment of yellow card reports does not support a link between changes in menstrual periods and covid-19 vaccines because the number of reports is low relative to the number of people vaccinated and the prevalence menstrual disturbances in general.7 However, the way yellow card data is collected makes it difficult to draw firm conclusions. Better-equipped approaches to compare the rates of menstrual change in vaccinated and unvaccinated populations are needed, and the US National Institutes of Health have made available $ 1.67 million (£ 1.2 million; 1) , 4 million euros) to encourage this important research.8

Menstrual changes have been reported after mRNA and adenovirus vector covid-19 vaccines, 1 suggesting that, if there is a link, it is likely to result from the immune response to vaccination rather than a specific component of the vaccine. Human papillomavirus (HPV) vaccination has also been associated with menstrual changes.9 Indeed, the menstrual cycle may be affected by immune activation in response to a variety of stimuli, including viral infection: in a study involving in menstruating women, about a quarter of people infected with SARS-CoV-2 experienced a menstrual disturbance.10

Biologically plausible mechanisms linking immune stimulation to menstrual changes include immunological influences on hormones that control the menstrual cycle11 or effects induced by immune cells in the lining of the uterus, which are involved in cyclical buildup and breakdown. of this tissue.12 Research exploring a possible association between covid-19 vaccines and menstrual changes may also help understand the mechanism.

Although the reported changes in the menstrual cycle after vaccination are short-lived, extensive research into this possible adverse reaction remains critical to the overall success of the vaccination program. The reluctance to vaccinate among young women is largely driven by false claims that covid-19 vaccines could harm their chances of future pregnancy.13 Failure to thoroughly investigate reports of changes menstruation after vaccination is likely to fuel these fears. If a link between vaccination and menstrual changes is confirmed, this information will allow people to plan for potentially altered cycles. Clear and reliable information is especially important for those who rely on their ability to predict their menstrual cycles to achieve or avoid pregnancy.

We’re still waiting for definitive evidence, but in the meantime, how should clinicians advise those who have experienced these effects? Initially, they should be encouraged to report any unexpected period changes or vaginal bleeding to the MHRA yellow card system. This will provide more comprehensive data to facilitate research on any link and signal to patients that their vaccine safety concerns are taken seriously, thus building confidence. In terms of management, the Royal College of Obstetricians and Gynecologists and the MHRA recommend that anyone reporting a period change that persists over several cycles, or new vaginal bleeding after menopause, be managed according to standard clinical guidelines for these conditions.714

An important lesson is that the effects of medical interventions on menstruation should not be an afterthought in future research. Clinical trials provide the ideal setting to differentiate menstrual changes caused by interventions from those that occur anyway, but participants are unlikely to report period changes unless specifically requested. Information on menstrual cycles and other vaginal bleeding should be actively sought in future clinical trials, including trials of covid-19 vaccines.