More than 30,000 women report disruption to periods after Covid jab - but changes ‘short-lived’

Thousands of UK women experienced disruption to their periods after Covid-19 vaccination, a new report reveals.

More than 30,000 women reported changes to their menstrual cycle after their jab, although the effects were “short-lived” and returned to normal after a single cycle, according to an article in the British Medical Journal (BMJ).

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No evidence jabs affect fertility

The opinion article written by Dr Victoria Male, lecturer in reproductive immunology, said there is no evidence that vaccination against Covid-19 affects fertility.

However, Dr Male said more research is needed to ensure the success of the vaccination rollout, as hesitancy among women has largely been driven by “false claims” the jab could harm their chances of future pregnancy.

She wrote: “Failing to thoroughly investigate reports of menstrual changes after vaccination is likely to fuel these fears.

“If a link between vaccination and menstrual changes is confirmed, this information will allow people to plan for potentially altered cycles.

“Clear and trusted information is particularly important for those who rely on being able to predict their menstrual cycles to either achieve or avoid pregnancy.”

While common side effects from Covid-19 vaccination, including a sore arm, fever and fatigue, are listed by the Medicines and Healthcare products Regulatory Agency (MHRA), changes to periods is not included.

Despite more than 30,000 reports of menstrual cycle disruption to the MHRA’s yellow card surveillance scheme, the cases are still too low to be added as a common symptom of coronavirus vaccination.

Dr Male added: “MHRA states that evaluation of yellow card reports does not support a link between changes to menstrual periods and Covid-19 vaccines since the number of reports is low relative to both the number of people vaccinated and the prevalence of menstrual disorders generally.

“However, the way in which yellow card data is collected makes firm conclusions difficult.

“Most people who report a change to their period after vaccination find that it returns to normal the following cycle and, importantly, there is no evidence that Covid-19 vaccination adversely affects fertility.”

The MHRA has said that period problems can be caused by stressful life events and added that changes to the menstrual cycle have also been reported after those infected with coronavirus, or are suffering with long Covid.

Dr Alison Cave, chief safety officer at the MHRA, said the regulator is “closely monitoring reports of suspected menstrual disorders” and stressed that the benefits of vaccination still outweigh the risks posed by Covid-19.

Period changes linked to immune response

Menstrual changes have been reported by women who received both mRNA vaccines, which include the Pfizer and Moderna jabs, as well as by those who had adenovirus vectored vaccines, such as AstraZeneca.

Dr Male said that the disruption to periods post-vaccination is likely a result of the immune system responding to the jab, rather than a specific vaccine component.

However, further research is needed to help understand the potential link between vaccines and disrupted menstrual cycles.

Dr Jo Mountfield, vice president of the Royal College of Obstetricians and Gynaecologists, added: “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.”

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