There are many testimonies from women observing a menstrual disorder after a Covid-19 vaccination, but the link seems difficult to establish scientifically.
Placed under surveillance last Friday by the Medicines Agency (ANSM), these menstrual disorders are, "to date", not linked to the Pfizer and Moderna vaccines.
"To date, we cannot establish a link between vaccination" against Covid-19 "and menstrual disorders", concludes the Medicines Agency (ANSM) in its point on the adverse effects linked to vaccines against Covid- 19, after analyzing some 300 reported cases.
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In recent weeks, "261 cases of menstrual disturbance, including 30 severe, were analyzed in women with a median age of 36.5 years" after an injection of the Pfizer BioNTech vaccine.
Moderna side, "49 cases of menstrual disorders, including 6 serious" were analyzed "in women of median age of 38 years".
"Consult a doctor" in case of persistent disorders
“The outcome is spontaneously favorable within a few days for the vast majority of cases.
We cannot to date establish a link between vaccination and menstrual disorders, the causes of these disorders can be multiple, explains the ANSM.
If these menstrual disorders persist, we invite vaccinated people to consult their doctor.
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As part of the enhanced surveillance system for #vaccines with @Reseau_CRPV, we are closely monitoring
#VaccinationCovid
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Key figures and pharmacovigilance report following the monitoring committee of August 5: https://t.co/JHGRD1eCHX pic.twitter.com / F3vEHlRWsL
- ANSM (@ansm) August 6, 2021
The ANSM had classified last week as a "potential signal" menstrual disorders - such as heavier or shifted periods compared to the usual cycle, or postmenopausal bleeding - after vaccination with Pfizer or Moderna.
The ANSM had also made a report to the European Medicines Agency (EMA).
For its part, the Pharmacovigilance Risk Assessment Committee (PRAC) of the European Medicines Agency also indicated on Friday that "no cause and effect link had been established at this stage between vaccines against Covid-19 and menstrual disorders ”.
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These disorders "are very common and can occur unrelated to a medical problem", underlines the PRAC, citing "stress and fatigue" among the possible causes.
The European medicines policeman adds that he has requested "additional data" from laboratories and "continues to monitor the subject" by analyzing the reports of adverse reactions and the available scientific literature.
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Some specialists suggest the hypothesis of a reaction of immune cells present in the uterine lining as a possible mechanism of action.
"Any immune activity can cause a slight or transient disturbance of the menstrual cycle without consequences in the medium and long term", said Thursday on France Inter the infectious disease specialist Karine Lacombe.
Specific follow-up for pregnant women
The ANSM also explains that it has set up "specific monitoring of the adverse effects reported with all vaccines in pregnant women", which has shown "no signal" of pharmacovigilance in this population.
More at risk of developing a severe form of Covid-19, they have been given priority for vaccination from the second trimester of pregnancy since April.
“Since July 21, 2021, the strategic orientation council of the vaccine strategy (COSV) proposes that their vaccination be possible during the first trimester of pregnancy,” recalls the ANSM.