Doctor calls for more studies into whether COVID-19 vaccines can cause period changes

Doctors have called for more studies into whether or not COVID-19 vaccines cause period changes after thousands of women have reported irregular menstrual cycles following the shots.

Dr Victoria Male, a lecturer in reproductive immunology at Imperial College London, said last year’s clinical trials should have looked for abnormal menstruation.  

At least 6,000 women in the U.S. report that their periods have come earlier than usual, felt heavier or just appeared irregular post-vaccination. 

Additionally, more than 35,000 women in Britain have complained of suffering irregular periods after being jabbed. 

Officials have yet to confirm there is a link between the shots and an irregular cycle, but Male said that the uterus has a lining with a high number of immune cells, which are likely activated by the vaccine and lead to irregular bleeding.

She added that investigating such a link could help prepare women for the possibility of irregular cycles and increase confidence in the shots.

‘Vaccine hesitancy among young women is largely driven by false claims that COVID-19 vaccines could harm their chances of future pregnancy,’ Male wrote in The BMJ..

‘Failing to thoroughly investigate reports of menstrual changes after vaccination is likely to fuel these fears.’ 

More than 6,000 women in the U.S. have reported heavier than normal or abnormal menstrual cycles to the CDC’s reporting system post-Covid vaccination

A doctor has called for more studies into the link between irregular periods and COVID-19 vaccines, saying investigations could calm fears that the vaccines are linked to infertility and increase confidence in the shots (file image)

A doctor has called for more studies into the link between irregular periods and COVID-19 vaccines, saying investigations could calm fears that the vaccines are linked to infertility and increase confidence in the shots (file image)

‘We’re seeing an association but that’s not necessarily causation…We have an opportunity here to study a women’s health issue,’ Dr Cynthia Brincat, chair of the department of obstetrics and gynecology at Rush University Medical Center, in Chicago, Illinois, told

‘We’re looking at something that impact women’s lives tremendously. We welcome anything opportunity to do that.’

According to a analysis of the Centers for Disease Control and Prevention’s (CDC) Vaccine Adverse Event Reporting System, there have been at least 6,047 reports of U.S. women reporting abnormal menstrual cycles.

However, this is likely a severe undercount because many women who experience abnormal periods will not report it to the CDC.

The most common complaint is heavy menstrual bleeding with 2,571 women reporting this symptom as of Thursday.

Other frequent reports include irregular menstruation, intermenstrual bleeding, menstruation delayed and abnormal uterine bleeding.

However, some women have experienced less common symptoms including an anovulatory cycle, which is when the release of an egg from the ovaries does not occur or superovulation, which occurs when a woman releases more than one egg in a month.  

Previously, CDC officials have said that none of the reports warrant concern.

‘At this time, CDC is not seeing any safety concerns that warrant additional surveillance of irregular menstrual symptoms reported to the Vaccine Adverse Event Reporting System,’ Martha Sharan, a public affairs officer for the CDC’s Vaccine Task Force said in an email to the Chicago Tribune.

She added that the the reports make up ‘a very small number’ of the more than 300 doses administered in the U.S.

However,  the National Institutes of Health (NIH) has awarded grants to five universities earlier this month to study whether or not there is a link between having abnormal periods and the COVID-19 vaccine.

The five studies will likely recruit between 400,000 and 500,000 participants, including adolescents, transgender women and nonbinary people. 

According to the NIH, there are several factors by which Covid immunizations can cause temporary menstrual cycle changes.

This includes stress related to the pandemic, lifestyle changes and even prior COVID-19 infection.

The NIH also suggests that the immune system’s response to the COVID-19 vaccine may briefly affect communication between immune cells and the uterus.

Gynecologists have previously told that cycle changes post-vaccination can occur – but that they are rare, typically resolve on their own within a month and without medication, and do not affect fertility.      

In the UK, more than 35,000 women have reported to the country’s Medicines and Healthcare products Regulatory Agency Yellow Card scheme that they have suffered irregular cycles after getting vaccinated.

Dr Jackie Maybin, a consultant gynecologist and senior clinical researcher fellow a the University of Edinburgh, said other vaccines, such as the HPV vaccine, have been known to disrupt periods with no noticeable impact on fertility.  

‘At this stage, it is difficult to be certain regarding the mechanisms causing these effects. It may differ from person to person,’ she said in a statement to the Royal College of Obstetricians and Gynaecologists.

Maybin also suggested that stress is playing a role – explaining that when the body is stressed, it prevents pregnancy to conserve energy. 

Brincat also said that, historically, it’s been show that stress impacts women’s health with other medications such as chemotherapy 

‘We’re also in a pandemic and there could be other changes such as loss of a job, supply chain issues that cause a change in the stress levels.’

Maybin says the COVID-19 may cause a change in stress levels by stimulating immune cells. 

‘This brain-level effect may explain some of the changes in menstruation observed during the pandemic, with Covid or with vaccination,’ she said. 

She added: ‘The resulting inflammation may transiently affect the ovaries, altering their hormone production over one or two cycles, resulting in irregular or heavier menstrual bleeding. 

‘The inflammation may also temporarily alter how the womb lining breaks down and sheds, causing a heavier period. 

‘These effects could lead to temporary changes in menstrual symptoms that should spontaneously resolve.’

Brincat said that if a menstruating patient came to her telling her about irregular cycles after getting the shot, she would say the following”

‘I would say first: “Congratulations on doing the best thing to your overall health by getting vaccinated.”   

‘Second thing I would say is: “Let’s look into this and do an investigation. You deserve an investigation.”‘