Covid vaccine and menstrual cycle disorders: a reassuring first study

A recent American study sheds solid light for the first time on the influence of Covid vaccines on menstruation. Rest assured, it is benign, punctual and has no effect on fertility.

Since the start of the vaccination campaign against Covid-19, a number of menstruating people have reported problems with their cycle after the injection. Some were indeed upset by late rules, occasional absence of rules, from heavier periods or abnormal bleeding after receiving at least one of the three doses.

The subject has been on the table for several months already and we have already addressed it in these columns, regretting that it is not taken seriously enough by the medical profession.

In France, the National Agency for Medicines and Health Products Safety (ANSM) in charge of pharmacovigilance does not establish, in its latest follow-up of adverse reactions from COVID-19 vaccines published on January 7, 2022 of causal relationship between the vaccines Comirnaty (Pfizer / BioNtech) and Spikevax (Moderna) and disruption of the rules.

However, the Agency does not deny the possibility and keeps its eyes open: “ Menstrual disturbances reported after vaccination with an mRNA vaccine are carefully monitored. (…) These effects occurred both after the first injection and after the second injection. Most of these are short-lived and self-limiting events. To date, the available data do not allow us to determine the direct link between the vaccine and the occurrence of these disorders of the menstrual cycle. These events remain under surveillance. »

Vaccine and the menstrual cycle: a reassuring first study

Is this enough to reassure menstruating people and instill consideration on the part of health professionals on the issue? Probably not. The fact is that pharmacovigilance is based on reports from menstruating and vaccinated people who have experienced cycle disorders. This declarative can be subject to various biases.

To establish a real causal link, we need something solid to put in our mouths and this requires minimal observational studies. A first study published on January 5, 2022 in the journal Obstetrics & Gynecology allows us to see more clearly and is reassuring.

The researchers tracked data from some 3,959 US people between the ages of 18 and 45 over 5 cycles using a menstrual cycle tracker app, not using birth control, and generally having a normal, regular cycle. 2,403 of them received an injection of the Covid vaccine (Pfizer, 55%, Moderna 35% and Johnson & Johnson / Janssen 7%) during the 3rd cycle and 1,556 of them were not vaccinated.

They were able to demonstrate that the two post-vaccination cycles were on average one day longer than the previous cycles, while they did not observe any change in cycle length in unvaccinated people. On the other hand, the duration of menstruation remains the same in the pre and post injection cycles.

A woman gets vaccinated // Source: Flickr/CC/SELF magazine

Stress linked to the vaccine and not to the pandemic

Far from the assumptions that preceded the publication of their study, the researchers specify that their results cannot be explained by generalized pandemic stress, since the control group did not observe any change.

They also report that their results are consistent with a recent analysis of 18,076 users of the Natural Cycles application (which presents itself as a contraceptive application most is not) before and during the pandemic, which also demonstrated no disruption of the cycle at the population level due to pandemic stress.

On the other hand, they provide a possible explanation for the phenomenon: mRNA vaccines cause an immune response which consists of a stress factor for the organism, which could temporarily affect the hypothalamic – pituitary-ovarian axis thus creating a slight disruption of the cycle. .

The fact that the lengthening of the cycle seems more frequent when the vaccine was administered during the follicular phase – that is to say during the phase which will determine the duration of the cycle and which can be affected by stress – seems to attest to this hypothesis. .

Results in favor of vaccination

The researchers report that this disturbance possibly caused by the vaccine is out of step with that potentially caused by a Covid-19 infection.

This can, according to them, permanently affect the hypothalamic-pituitary-ovarian axis and therefore have long-term consequences. Thus, their results are reassuring and strongly advocate the vaccination of menstruating people. However, the disruptions of the menstrual cycle related to mRNA vaccines against Covid-19 are not fully understood.

Questions to be clarified

The researchers do not explain the reports of exacerbated menstrual symptoms, unexpected bleeding, or qualitative and quantitative changes in flow. This lack of data, as well as all those relating to cycle disruptions during this pandemic period, invites a serious rethinking of the impact of covid on menstruation and its consequences, failing which women could again experience gender inequalities.

“Lack of high-quality research on Covid-19 and the menstrual cycle reflects the broader focus of medical research, which does not prioritize women’s health »

As an article in The International Journal of Epidemiology in December 2021: ” The lack of high-quality research focusing on Covid-19 and the menstrual cycle reflects the broader focus of medical research, which does not prioritize women’s health, especially outside of the context of pregnancy. The discovery that menstrual cycles appear to have been affected by the Covid-19 pandemic could have significant implications for society, gender-based inequalities, and post-Covid economic recovery. »

And to conclude: ” More research is needed to help understand and mitigate the impacts of the pandemic on menstrual health, which could help minimize gender-related health and social inequalities. The pandemic has also highlighted the need for more research to better understand how external environmental factors can influence the menstrual cycle and how the menstrual cycle can interact with other aspects of health in a two-way fashion. »

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