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An opinion piece, published in The BMJ, discusses menstrual changes after covid-19 vaccination.
Dr Jackie Maybin, Senior Clinical Research Fellow and Consultant Gynaecologist, MRC Centre for Reproductive Health, University of Edinburgh, said:
Is this saying there is a causal link between the vaccine and menstrual changes? Why do we think there may be a link?
“No, this paper is not stating there is a causal link between the vaccine and menstrual cycle, but sensibly suggests that any such potential link should be properly researched.
“At this stage, it is difficult to be certain regarding the mechanisms causing these effects. It may differ from person to person. The brain, ovaries and womb interact to control the menstrual cycle. Menstrual disturbance may be due to effects on the part of the brain that controls the reproductive hormones, effects on the ovaries or effects directly on the lining of the womb (which is what is shed during a period).
“In times of stress, the female system is designed to temporarily downregulate to prevent against pregnancy and conserve energy. This brain-level effect may explain some of the changes in menstruation observed during the pandemic, with COVID-19 or with vaccination. The COVID-19 vaccination itself is designed to initiate an immune response in the body to protect against future COVID-19 infection. 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. It is important to emphasise that any effects of the vaccine are likely to be short lived and much less severe than those associated with COVID-19 infection. Women who are called for the vaccine shouldn’t be deterred from attending.
Do you agree that even though the MHRA say the yellow card system says the data does not support a link, a link may still exist and needs to be addressed using a different approach?
“It is brilliant that the MHRA are collecting this data and those experiencing menstrual disturbance following vaccination should report their symptoms via this system (https://coronavirus-yellowcard.mhra.gov.uk). However, it would be wonderful to see the inclusion of menstrual symptoms into the existing and future clinical trials in this area to minimise reporting or selection bias e.g. underreporting as people are unaware of the MHRA reporting scheme or those experiencing the effect being the only ones responding. Other confounders should also be examined, e.g. use of hormonal contraceptives verses effects on physiological menstrual cycles.
Do any other vaccines have this effect? How likely is it that COVID vaccines do this too?
“Yes, similar short-term menstrual effects have been reported following HPV vaccination and Hepatitis B vaccination. This suggests that effects are due to either the stress of receiving a vaccination or due to the necessary immune process that occurs to initiate protection. Previous reports are of transient effects on menstrual symptoms and there is no evidence of an impact on fertility.
How worried should we be if the reported changes are short lived?
“Women who are experiencing persistent menstrual changes, very irregular bleeding or who have any vaginal bleeding after the menopause should speak to their doctor to exclude other serious causes. Otherwise, the available evidence supports a short lived effect and there appears to be no evidence of a negative impact on fertility.
What would you say to anyone considering not taking the vaccine for fear of changes to the menstrual cycle and/or fertility?
“I can understand that people will have anxieties and would recommend that they speak to medical professionals about their concerns. The British Fertility Society have published very useful information about the COVID vaccination in those wishing to conceive (https://www.britishfertilitysociety.org.uk/wp-content/uploads/2021/02/Covid19-Vaccines-FAQ-1_3.pdf). There are many reports of menstrual disturbance in those who contract COVID-19 and in those experiencing Long COVID. It is very likely that any effects from the vaccine will be much less severe and more short-lived that COVID-19 itself and any protection from COVID-19 is likely to decrease the risk of experiencing these symptoms overall. I would encourage women not to be deterred from attending for the vaccination when called.”
Dr Gemma Sharp, Senior Lecturer in Molecular Epidemiology, University of Bristol, said:
Is this saying there is a causal link between the vaccine and menstrual changes? Why do we think there may be a link?
“This paper is saying there might be a causal link between vaccination (not specifically COVID-19 vaccines) and menstrual changes, and this requires further research to put people’s minds at rest. However, it is very important to note that for most women, cycles return to normal quickly.
“Since the COVID-19 pandemic started, many women have been discussing on social media that their periods have changed. These changes include altered menstrual duration, frequency, regularity and volume (heavier bleeding and clotting) and worsened premenstrual syndrome. There are many reasons why this could be. Increased stress and weight changes are known to affect the menstrual cycle. Viral infection and illness (including, potentially, with COVID-19) can also instigate menstrual changes. Vaccines are another potential trigger, because, similarly to infections, they can cause short term, reversible disruptions to the immune system, which can throw the menstrual cycle off kilter. But this applies to all vaccines, not just COVID-19 vaccines. And these changes are likely to last for one or a small number of cycles, with no reason to suspect any lasting effects or effects on fertility.
Do you agree that even though the MHRA say the yellow card system says the data does not support a link, a link may still exist and needs to be addressed using a different approach?
“It is biologically plausible that vaccines can affect menstrual cycles through short term disruptions to the immune system. Although the number of people reporting a change to the Yellow Card system is low relative to the number of people being vaccinated, there are still over 30,000 people who were concerned enough to report their menstrual changes. Further research is needed to put people’s minds at rest. Scientific questions such as this one are often best tackled from multiple angles using multiple methods – if different approaches give the same answer, we can be more confident the answer is correct.
Do any other vaccines have this effect? How likely is it that COVID vaccines do this too?
“Too few vaccine trials collect data on menstrual cycles, but one study has shown that vaccination against HPV was associated with short term changes to the menstrual cycles of some women. It is biologically plausible that vaccines can affect menstrual cycles through short term disruptions to the immune system, but there is no reason to suspect these changes would be persistent or have any lasting effect on fertility.
How worried should we be if the reported changes are short lived?
“Short-lived changes to the menstrual cycle are part of the body’s normal response to things like stress and immune disruptions. There is no reason to suspect these changes would indicate any long term effects on health or fertility.”
Dr Jo Mountfield, Vice President of the Royal College of Obstetricians and Gynaecologists, said:
“We understand that any changes to periods following a COVID-19 vaccine can be concerning. We want to reassure women that any changes generally revert back to normal after one or two cycles. We would encourage anyone who experiences heavy bleeding that is unusual for them, especially after the menopause, to speak to a healthcare professional.
“There is no evidence to suggest that these temporary changes will have any impact on a person’s future fertility, or their ability to have children. It is important to get vaccinated as the best protection against coronavirus. This is especially important if you are planning a pregnancy, as we know unvaccinated pregnant women are more at risk of becoming seriously ill from COVID-19.
“We support calls for more research to understand why women may be experiencing changes to their menstrual cycle after having the vaccine.”
Dr Sarah Hardman, Specialty Doctor SRH, Menopause Lead Chalmers Centre, and Co-Director of the FSRH Clinical Effectiveness Unit, said:
“There isn’t evidence to indicate that fertility is affected by either Covid-19 infection or Covid-19 vaccination.
“There have indeed been reports of disturbance in menstrual bleeding pattern around the time of both Covid-19 vaccination and Covid-19 infection. Some reports relate to individuals using hormonal contraception and some relate to individuals having natural menstrual cycles. Most cases appear to resolve spontaneously and rapidly, which is generally reassuring for subsequent fertility. There is no indication that effectiveness of hormonal contraception is affected.
“The available evidence does not confirm or exclude either Covid-19 infection or Covid-19 vaccination as causes of change in bleeding pattern. Menstrual disturbance is common and cases may well have occurred coincidentally around the time of Covid-19 illness or vaccination. There isn’t a clear indication of how the infection or vaccination would cause the change. The fact that there are many reports of altered bleeding pattern may simply reflect normal variation in bleed pattern amongst the millions of individuals that have had Covid-19 infections and Covid-19 vaccination.”
‘Menstrual changes after covid-19 vaccination’ is an opinion piece by Dr Victoria Male published in The BMJ at 23:30 UK time Wednesday 15 September
All our previous output on this subject can be seen at this weblink:
www.sciencemediacentre.org/tag/covid-19
Declared interests
Dr Jackie Maybin: No conflicts of interest to declare
None others received.