Changes in the rule after the covid vaccine: scientists see a trend to more bleeding, but temporary and not worrying

More than 5,000 million people in the world have received the covid vaccine.

Prick by prick, the success that these drugs promised in clinical trials quickly landed on the street: according to a study published in

thanks to them, about 20 million lives were saved.

The toll to pay, in the vast majority of cases, were mild side effects, such as headaches or general malaise, although its effects beyond those predicted in previous studies are still being investigated.

Among women, for example, the controversy persists about the impact (or not) on the menstrual cycle, with sometimes contradictory data and experiences on the street that were not seen —or were not even asked— in clinical trials.

Along these lines, a survey of nearly 40,000 people published today in

sheds a little more light on the impact on menstruation: 42% of those interviewed with regular menstrual cycles reported more abundant bleeding after the puncture.

This does not mean that it is the cause, but it does draw "a trend", the researchers point out, which will serve to better inform women, although this phenomenon is temporary and not worrying, they qualify.

Vaccines remain safe and recommended, they insist.

It was her own personal experience that opened the door for Katharine Lee, a professor in the Department of Anthropology at Tulanem University, to study the eventual impact of vaccination on menstruation.

Both she and Dr. Kathryn Clancy, an anthropologist at the University of Illinois, both co-authors of the study, suffered from "unstable" menstruations after receiving the vaccine, but when they started looking for why that was happening, they found little information, explains Lee by mail. email: “After seeing how many people were sharing similar stories, we wanted to collect information to give people an avenue to be heard and characterize what trends there might be in the data so we could develop hypotheses about what might be happening.”

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In total, 39,129 people — 90% identified only as women and 9% as gender diverse — participated in the survey.

And the answers showed that 42% of people with a regular period reported an increase in menstrual bleeding after vaccination, while another 44% found no change in their bleeding pattern.

Research suggests, however, that there are groups more likely to experience heavier bleeding after vaccination, such as those who are white, Hispanic, or Latino, older, have been pregnant in the past, or have underlying menstrual disorders , such as endometriosis or polycystic ovary syndrome, among other variables.

The survey also reveals that, among those who do not menstruate, 71% of those taking contraceptives that suppress ovulation, two-thirds of postmenopausal women and more than a third of those taking gender-affirming hormones also had bleeding.

The researchers point out that these findings serve to show a "trend", but, as they are observational studies, the causality of the increase in bleeding with vaccination cannot be confirmed, nor can the prevalence of the survey be extrapolated to the general population.

"There is almost certainly a selection bias in our sample, meaning that the people who participated were probably more likely to have experienced a menstrual change than the general population," admits Lee, but, in turn, defends the methodology. of the study and its solvency, even if it is about subjective perceptions of the participants: “Science has to start somewhere, and systematic observation and recording of information are incredibly important steps.

It is a mistake to assume that people's observations about their own bodies are wrong, and it is disrespectful to start from a place where people are not believed.

Surveys are incredibly important ways of understanding people's experiences and underpin much medical and clinical research."

Neither rare nor dangerous

In any case, the researchers warn, "changes in menstrual bleeding are not uncommon or dangerous."

In fact, these changes in menstruation have already been reported in old studies associated with the injection of the typhoid, hepatitis B or human papillomavirus vaccine, recalls Lee's research.

The imbalances described in her survey, moreover, are usually temporary and last a couple of cycles: “What we are talking about here is a temporary change in menstruation, not a menstrual disorder.

A menstrual disorder is usually a pathology, like endometriosis or fibroids, and the vaccine does not cause that.

What it can cause—in some people, but not all—is a temporary interruption in the normal cycle”, he qualifies.

On whether these results can serve as ammunition for anti-vaccine movements, Lee is blunt: "We are not concerned about this phenomenon and we are in favor of the vaccine."

And if an unvaccinated woman came to her to ask what to do, the anthropologist does not hesitate either: "It is much more likely that you will have prolonged effects on your cycle if you contract covid and it seems that many people with persistent covid also have prolonged menstrual changes."

The anthropologist defends the safety of vaccines: “I think that people can understand the difference between a secondary effect, such as fever, fatigue, headache after vaccination, of something that affects safety.

A couple of irregular periods should be understood as a side effect of a vaccine, and just like you can take acetaminophen if you get a fever and headache after a vaccine,

“We are not concerned about this phenomenon and we are in favor of the vaccine”

Katharine Lee, Tulanem University

Lee's study agrees with what is seen in consultations, points out Santiago Palacios, spokesman for the Spanish Society of Gynecology and Obstetrics: “The experience that we were all seeing is that it is true that menstruation is altered.

From a medical point of view it is not alarming and we do not give it relevance, but it does create concern in the patient and her quality of life is affected.

The importance of this study is that there are 40,000 people and they come to endorse what was known”.

Cristina González Cea, a gynecologist at the Hospital de Santiago de Compostela, sees “a very clear causal relationship between vaccines and covid infection with these menstrual disorders”: “In January, after the injection of the third doses, we saw a flood of patients in consultations with these phenomena of abundant bleeding or absence of periods.

Silvia Agramunt, a gynecologist at the Hospital del Mar in Barcelona, ​​points out that it is a “useful study to be able to inform before getting vaccinated, so that they can assess it, but it is not a deterrent”.

"If a patient comes to me who is not vaccinated, I would simply explain to her that, just as you can have a fever, this can happen, but, for now, there is no data that says that it can have a long-term impact," adds the specialist. , who admits that menstrual changes after vaccination is a topic that has been talked about a lot.

The researchers emphasize that, for now, no effects on fertility have been seen and they dismiss the malicious voices that associate menstrual imbalances with the risk of infertility.

"We emphasize that changes in menstrual bleeding of this nature are generally not indicative of changes in fertility," the study researchers say.

For Agramunt, the imbalances are more like the effect "of the morning after pill, which also generates deregulation and has an impact, but temporarily."

controversial phenomenon

Lee and his colleagues' study shines a spotlight on a controversial phenomenon.

First of all, because it was not studied in the initial trials with the vaccines — "The protocols do not monitor important adverse events for more than seven days and the additional follow-up communications do not ask about the menstrual cycle or bleeding," the researchers explain in the study-.

And the scientific literature on the subject is diverse, with studies pointing in both directions.

The European Medicines Agency, for example, concludes that there is insufficient evidence to establish a causal relationship between the covid vaccine and reported cases of missed menstruation.

But an article published in the

, on the other hand, considered it "plausible" that there were changes in menstruation and bleeding and called for studying them to guarantee the success of vaccination campaigns: "Vaccine reluctance among young women is largely due to false claims that covid vaccines could hurt your chances of future pregnancies.

Failure to fully investigate reports of menstrual changes after vaccination is likely to fuel these fears," said lead author Victoria Male, a research fellow in the Department of Metabolism, Digestion and Reproduction at Imperial College London.

Another American study saw a slight change in menstrual cycle length of less than a day and a Norwegian investigation, also through surveys of participants, concluded that there was a significant increase in menstrual imbalances after vaccination, especially "bleeding more intense, of longer duration and for short intervals between menstruations”.

If a causal relationship is found, the explanation of why it happens is still up in the air.

"We have no idea of ​​the mechanism of action by which something happens," admits Palacios.

There are several hypotheses.

From the Galician capital, González Cea has begun to investigate precisely why this is happening and points to a viral action that alters hormonal function: “We have collected samples from 150 patients with post-vaccine or post-Covid bleeding episodes and, in the ultrasounds, we found sustained ovulation outside the cycle and a rise in estrogen.

Our theory goes to hyperovulation.

We believe that it may be the virus that causes stimulation of hormone receptors.”

Agramunt also raises the hypothesis of inflammation and coagulation: "Supposedly, the vaccine activates the immune system and can induce changes in coagulation and that the uterus repairs the wall poorly when it expels the endometrium."

Along the same lines, Lee points out: “The menstrual cycle is supposed to respond to stressors.

We know that the rules vary based on things like energy stress—like increasing exercise without increasing food intake—and immune stress—like having the flu.

The vaccine is an immune stressor because that's how it works by activating the immune system to protect you, and the uterus is an immune organ."

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