July 2, 2022

“No direct link” between vaccination and menstrual disorders

While the Omicron variant, more contagious, is gradually replacing Delta around the world – in France, Omicron is now believed to be the source of 20% of new contaminations – the vaccine booster campaign against Covid-19 is accelerating. More than 20 million people had thus received a booster dose in the country, Tuesday, December 21.

On the same day, the Medicines and Health Products Safety Agency (ANSM) published its new update on the monitoring of vaccines and their side effects. One of them had particularly worried women this summer, the latter reporting menstrual disorders after a vaccination against Covid-19. Since the start of the vaccination campaign, 4,432 cases have been identified after receiving a dose of messenger RNA vaccines from Pfizer-BioNTech or Moderna.

After a first study of these potential effects at the end of the summer, this new point concerns the reports issued until November 4. In its general conclusions, the ANSM notes that, despite a “Significant number of notifications” received, “The available data do not allow to determine the direct link between the vaccine and the occurrence [de ces perturbations menstruelles] ». Information confirmed by a pharmacovigilance manager from the European Medicines Agency (EMA) during a press briefing on Tuesday.

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Many potential explanations

In the reported cases, it is “Mostly non-serious, short-term and spontaneously resolving events”. These disturbances of the menstrual cycle are manifested mainly by abnormal bleeding (metrorrhagia – bleeding outside the rules – or menorrhagia – abnormally long periods) and by delayed periods and amenorrhea (absence of periods), specifies the situation.

Object “Careful monitoring”, the disorders seem to affect all women, from young adolescents with still immature cycles to some postmenopausal patients. The authority believes that they could be linked at the same time to the vaccine, to the act of vaccination, to the unprecedented situation generating anxiety and stress or to a simple coincidence.

In its more precise pharmacovigilance survey concerning the Moderna vaccine, the ANSM quotes an editorial from the journal British Medical Journal (BMJ) on data from the English Medicines Agency which leans more towards “An effect linked to the immune reaction to vaccination rather than a reaction specific to the vaccine”. The latter could thus “Influence the hormones involved in the menstrual cycle or the mediators acting on uterine tissues during the cycle”.

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In addition, the pharmacovigilance study for Pfizer-BioNTech notes that data exists on the impact of Covid-19 on the menstrual cycle: “Menstruation disorders are reported without it being possible [non plus] whether it is the infection, the stress or changes in behavior ”.

Abroad, similar reports

As the events reported after vaccination are very varied and often not very precise, they constitute “A potential signal that should be analyzed in collaboration with gynecologists” of the National College of Obstetrician Gynecologists of France (CNGOF), continues the point of the ANSM.

If no link can yet be established between vaccination and disruption of menstrual cycles, similar reports have however been made outside French borders, in Spain or in the United Kingdom. The UK Medicines and Health Products Regulatory Agency (MHRA) reports a total of some 44,200 reported cases with heavier-than-normal periods, delayed periods and abnormal vaginal bleeding. But the number of reports “Is low compared to the number of women who have received a vaccine against Covid-19 and the general frequency of menstrual disturbances”, notes the MHRA.

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The results of a survey presented on Tuesday by the Norwegian Institute of Public Health, carried out among more 6,000 women aged 18 to 30 years before the injections of the first two doses of a vaccine against the Covid-19, suggest that the Menstrual cycle disorders are actually more common after vaccination. But the conclusions of this study, which has not yet been submitted to a peer review committee, still need to be considered with caution and “Must be confirmed by other studies”, emphasized the authors.

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