Original article (in Croatian) was published on 01/10/2021
Changes in the menstrual cycle are temporary, and it is still being investigated whether they are directly related to vaccination.
The BBC reported that more than 30,000 women in the UK had reported changes in their menstrual cycle, or unexpected vaginal bleeding, by early September, after receiving the Covid-19 vaccine.
Similar reports have been previously recorded in the USA, and it has been confirmed to us from domestic medical circles that changes have been recorded in our country as well. Doctors emphasize that these are temporary changes in the cycle that appear a month or two after the vaccine so that, according to the patients’ experiences, the cycle then stabilizes.
Following the BBC’s reporting, the Royal College of Obstetricians & Gynecologists (RCOG) and the Faculty of Sexual and Reproductive Healthcare (FSRH) issued a joint statement. The British government’s website states that the UK’s Medicines and Health Products Control Agency said in August there was no evidence that changes in the cycle were a direct result of vaccination, based on a relatively small percentage of reports in relation to the number of people vaccinated in the country (almost 45 million people have been fully vaccinated in the UK to date), as well as to the usual variability of the cycle.
The reaction of RCOG and FSRH also reminds us that, for now, there is no evidence of a direct connection, but the possibility of that connection is not denied, and the further research on this topic is welcomed.
Referring to the reported cases, Dr. Jo Mountfield, Vice President of the RCGO, stated that everything should return to normal before vaccination within one or two cycles, calling on women who have particularly heavy and unusual bleeding, especially after menopause, to contact their doctors.
The consequence of the body’s immune response?
“There is no evidence that these temporary changes could have any impact on future fertility, or the ability to have children. It is important to get vaccinated because it is the best protection against coronavirus. This is especially important for those who are planning a pregnancy because it has been determined that pregnant women are at a higher risk of a more severe form of Covid 19”, she stated.
Dr. Jackie Maybin of the University of Edinburgh noted that there had been many reports of changes in menstruation after vaccination, including changes in the frequency, duration and extent of bleeding. However, such changes at this time, in her view, cannot be unequivocally attributed to a direct link to vaccination, and given that they may also be due to the wider impact of the pandemic.
“At this point, it is difficult to say with certainty which mechanisms cause such consequences because they can vary from person to person. The brain, ovaries, and uterus interact to control the menstrual cycle. Changes in menstruation can be the effect of the part of the brain that controls reproductive hormones, the effect on the ovaries or the uterine wall”, said Dr. Maybin, explaining that the female body is designed to react in times of stress to temporarily prevent pregnancy and thus conserve energy.
Covid vaccines are designed to stimulate an immune response, and triggering that response can affect the ovaries, altering normal hormone production over a cycle or two, resulting in more extensive menstrual bleeding. The immune response can also affect the uterine wall and cause heavier bleeding.
A quarter of Covid patients record cycle changes
The BBC article is based on the opinion of reproductive immunology expert Dr. Victoria Male of Imperial College London, who said in her article that a direct link between vaccines and changes in the menstrual cycle is likely and called for scientific research to determine exact mechanisms. She argues that the fact that these changes are relatively rare in relation to the number of vaccinated is not really reliable because changes in the menstrual cycle are generally not officially reported.
The question of possible changes in the menstrual cycle was not considered in clinical trials of the vaccine (either due to the gender insensitivity of the study creator or due to increased attention to possible more dangerous life-threatening side effects), so they were not originally registered as vaccine side effects.
The possible cause of changes in the cycle is the immune response to the vaccine, not the composition of the vaccine itself – given that the changes were observed after all four widely approved vaccines, and the composition of Pfizer and Moderna differs from the vector vaccines on which AstraZeneca and Johnson & Johnson vaccines are based.
Dr. Male states that changes in the menstrual cycle were recorded after the HPV vaccine, but also after the disease of Covid. An earlier study showed that 25 percent of women of reproductive age who survived Covid-19 experienced a change in volume, and 28 percent in the frequency of menstruation. The change was mostly about reduced volume and extended cycle. The changes are explained by a possible decreased ovarian function that has returned to normal levels soon after recovery from the disease.
In her article, Dr. Male emphasizes that previous research has shown that vaccines do not affect fertility. In clinical trials conducted so far, both desired and unwanted pregnancies occurred in equal percentages in vaccinated and non-vaccinated women (1, 2, 3, 4, 5).
Although the reported changes in the menstrual cycle after vaccination were short-lived, serious research into such reactions is also necessary for the overall success of the vaccination campaign, Dr. Male notes. Hesitation among younger women is fueled mainly by false claims that vaccines reduce the chances of future pregnancies. Missing the opportunity to explore the mechanisms that lead to changes in the menstrual cycle can only heighten those fears, warns Dr. Male. On the other hand, if a direct link is established between vaccination and changes in menstruation, this information will help in planning an early pregnancy or avoiding it.
Following similar remarks in its field, the US National Institute of Health has allocated $1.67 million to institutions that should investigate in detail within a year the possible link between the Covid vaccine and changes in the menstrual cycle and the duration of such changes, and determine the mechanisms that lead to these changes.
