Anti-Covid vaccine and period: a study points out their direct relationship and explains how it happens

• Analysis A new study confirms the link between anti-Covid vaccination and increased menstrual cycle length

• Study The Covid vaccine increased menstrual bleeding in 42% of women

As vaccination has been extended to younger age groups, some women have noted menstrual changes after vaccination and concern has arisen and the need for research and robust data.

But not only have menstrual changes been reported in association with Covid vaccines, but also against other pathogens, so a secondary objective of this work is to

.

This is how the article published by

magazine entitled

, a review of what we know to date.

By April 2022, both the US and UK vaccine adverse event reporting systems had received tens of thousands of reports of

.

These systems are effective in detecting serious adverse events, such as the rare bleeding disorder immune thrombocytopenia associated with adenovirus-vectored vaccines or myocarditis as a rare adverse event associated with mRNA vaccines.

However,

.

In addition, in the case of menstrual cycles, it is a greater challenge to determine to what extent the changes are attributable to the Covid vaccines since

due to multiple factors.

In this sense, according to a study by the Norwegian Institute of Public Health (NIPH)

, even before vaccination.

Another US study using a menstrual cycle tracking app reported a

.

All of this underlined the need for formal approaches, with unvaccinated comparison groups, to identify changes specifically associated with the vaccine.

The findings have been consistent.

Thus, vaccination against Covid is

: according to different American studies, the duration of the cycle returned to normal after two cycles.

A British study also found a small but significant increase in duration only in cycles in which a dose of vaccine was given.

Regarding bleeding, the Norwegian NIPH study also found an

.

The evidence has become clear that vaccination against Covid temporarily alters menstrual cycles, but

?

The type of vaccine does not affect a woman's chance of experiencing changes in her menstrual cycle or flow, suggesting that

and not a specific component of the vaccine.

Proof of this would also be that before the Covid vaccines,

(HPV) vaccines.

Two studies have addressed the hypothesis that menstrual changes after vaccination against Covid are associated with the activation of the immune response, but with conflicting results.

One of them found no association between the magnitude of side effects and changes in cycle length or flow.

But the other found that women who experienced

than usual.

Both have weaknesses: in one case, the cohort is small (the number of participants);

the other case is based on whether participants accurately recall their experiences and is influenced by how likely respondents are to recall other side effects if they noticed a menstrual change.

Two possible biological mechanisms

Two biologically plausible mechanisms have been proposed by which immune stimulation could cause menstrual changes: innate immune responses could transiently interfere with

, or it could affect

, which control the breakdown and regeneration of this tissue throughout the cycle.

In support of the

mediated

, women in whom the ovarian hormones estrogen and progesterone are supplied exogenously by combined hormonal contraception

.

In addition, vaccination within the menstrual cycle affects whether the cycle length is increased.

The menstrual cycle is divided into two phases: the follicular phase, which occurs before ovulation and can be prolonged by hormonal changes, and the luteal phase, which occurs after the release of the ovum and has a more constant duration.

If the menstrual changes are mediated by immune effects on the control of ovarian hormones, vaccination would be expected to prolong the follicular phase, but this can only occur if the vaccines are administered during this phase.

Supporting the possibility that the Covid-19 vaccine affects

, a survey of more than 27,000 women found that

.

This could suggest that impaired tissue repair, which is mediated by immune cells in the womb and may be less effective in older people, is the mechanism by which the Covid vaccine increases menstrual flow.

Therefore,

and could be consistent with effects mediated by ovarian hormones (affecting cycle length) and endometrial repair (affecting menstrual flow).

More research is required to definitively identify the pathways involved.

Menstruation and Covid infection

Does SARS-CoV-2 infection also affect menstruation?

While studies can track before and after vaccination,

(asymptomatic), making it difficult to define a uninfected control group.

In studies in the early stages of the pandemic,

reported changes in their periods after Covid infection, but one was done in hospitalized with Covid, another in women with persistent Covid and was not found. included an uninfected control group in none, so these

.

Another study found no effect of infection, but also had various limitations in detecting small or temporary effects.

As lessons, it can be noted that although more than half of the world's population menstruates at some point in their lives,

.

Menstrual cycle tracking

have proven effective because they have

and collecting data in real time mitigates recall bias.

But these app users are not representative of the global population because they

, and young, white, and highly educated women are overrepresented.

They also know that they are vaccinated and that can affect their perception of aspects of menstruation, so including a blind control group, as in vaccine trials, avoids these problems.

These advances also open up

.

It is important to recruit people who are already planning to receive a vaccine dose, which avoids the ethical challenges of giving participants an immune boost purely for experimental reasons.

In addition to looking at how immune stimulation affects female reproductive parameters,

There is a chance, finally, to start making real progress in an area that has historically been understudied.

According to the criteria of The Trust Project

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