Menstrual changes from Covid jabs are only temporary, top expert insists


Menstrual changes from Covid vaccines are only temporary and don’t leave women infertile, a leading expert insisted today.

Tens of thousands of women have complained about late or unusually heavy periods after getting jabbed. Anti-vaxx campaigners have leapt on the reports, using them to peddle fears that vaccines may, therefore, affect fertility. 

But a top fertility specialist has now debunked the concerns, insisting that the actual evidence on the topic is ‘reassuring’. 

Dr Victoria Male, who is based at King’s College London, reviewed findings from two new studies involving over 10,000 women. 

While Covid jabs have been found to make periods slightly late or heavier than normal British experts say new studies show the changes are both minor and quickly reverse

While Covid jabs have been found to make periods slightly late or heavier than normal British experts say new studies show the changes are both minor and quickly reverse

What’s normal for a period? 

A period is the part of the cycle when a woman bleeds from her vagina for a few days.

For most women this happens every 28 days or so but its not unusual for the cycle to be between 21 or 40 days for individual women. 

Periods tend to last between three and to eight days, with the average being five.  

Bleeding tends to be heaviest in the first two days.

Some women have irregular periods where the cycle is inconsistent.

For some this is natural and nothing to worry about, but the NHS advises women to contact their GP if: 

  • if their periods suddenly become irregular and they are under 45-years-of-age
  • their periods come more often than every 21 days and less often than every 35 days
  • their period lasts longer than seven days
  • there is a difference of at least 20 days between the shortest and longest menstrual cycle

Writing in the British Medical Journal, she said: ‘Changes to the menstrual cycle do occur following vaccination.’

The problems have also been linked to other jabs, and illnesses including Covid itself, as well as factors like contraceptive use and stress. 

But Dr Male said the menstrual changes caused by the Covid jab were ‘small’ and ‘quickly reverse’. 

The first study used data from nearly 4,000 American women who had logged at least six menstrual cycles on a period tracking app.

Of this group, 2,403 received Covid jabs, while the other 1,556 did not.

Data showed the first coronavirus vaccine had no impact on the timing of the next period, overall.

Yet the second jab was associated with a delayed period of just under half-a-day, on average. But some saw far greater delays.

The women most affected were a group of 358 who received both Covid vaccines in the same mensural cycle.

Of this group 11 per cent experienced a change in cycle length of more than eight days, according to researchers form the Oregon Health & Science University. 

However, all vaccinated women saw their periods return to their normal length two cycles after being jabbed.

The second study Dr Male referred to was from a survey of 5,688 Norwegian women. 

Participants were all asked if they had experienced any changes with their menstrual cycles, both before and after their first and second Covid jab.

Thirty-nine per cent said they saw a change after their first vaccine dose, and 41 per cent reported a change after their second dose.

The most commonly reported change was a heavier than normal period. 

But Dr Male said considering 38 per cent of women report a change to their normal cycle before getting a Covid jab, the increase to menstrual cycle disruption from vaccination appeared to be minor.

However, she added the findings had limited application to the UK because of rules that make it unlikely for women to have received two jabs in the same cycle.

Covid vaccines do NOT affect fertility in women who go through IVF or conceive naturally, study finds 

Coronavirus jabs do not affect a woman’s ability to conceive a child, another study suggests.  

Researchers in New York monitored more than 2,000 women undergoing in-vitro fertilisation (IVF) or fertility treatment.

Rates of pregnancy were ‘the same’ among unvaccinated women and those double-jabbed with Pfizer or Moderna. 

The researchers said the findings add to ‘ever-increasing evidence’ the jabs do not interfere with fertility, despite misinformation being common online.  

Lead author Dr Devora Aharon added that there was no difference in ‘egg quality or embryo development’ between women who were jabbed and un-jabbed. 

She said: ‘Our findings that vaccination had no impact on these outcomes should be reassuring to those who are trying to conceive or are in early pregnancy.’ 

Vaccine hesitancy has been common among young women and expectant mothers due to concerns about fertility that were preyed upon by anti-vaxx groups. 

But despite billions of women vaccinated around the world, there has not been any uptick in miscarriages or significant dips in birthrates. 

And a growing number of studies have failed to spot a mechanism for the vaccines to interfere with fertility or pregnancy. 


In the UK people need to wait eight weeks between their first and second vaccines, and the average menstrual cycle occurs every four weeks. 

In contrast the US only advises a a 21-to-28-day wait between Covid jabs, depending on what vaccine people received. 

Dr Male said results from a UK study which used the same app as the US research is due out soon.

This should provide some clearer insight into how the UK’s different vaccine regime has effected menstrual cycles, she said. 

Data from the UK’s Medicines and Healthcare Products Regulatory Agency indicates 37,000 British women have reported a change to their period after a Covid jab.

Dr Male said more work needed to be done to determine the exact mechanism that causes the Covid jab to have affect women’s periods.  

‘Medically, we must also determine whether any group is particularly vulnerable — for example, those with pre-existing gynaecological conditions — so they can be counselled appropriately,’ Dr Male said. 

She added that the potential for vaccines to impact fertility was one of the key concerns of the jab-hesitant public. 

‘The work that has been done represents a step in the right direction,’ she wrote in the journal. 

‘But the fact it has taken us so long to get here reflects the low priority with which menstrual and reproductive health is often treated in medical research.

‘The widespread interest in this topic highlights how pressing a concern this is for the public. It’s time we started listening to them.’   

The length of the menstrual cycle varies between individual women, but the average is every 28 days. 

However, cycles as short as 21 days or as long as 40 are not considered unusual.   

The NHS advises women to contact their GP if their periods are irregular in certain situations. 

These include: if their periods suddenly become irregular and they are under 45-years-of-age, their periods come more often than every 21 days and less often than every 35 days, their period lasts longer than seven days, and there is a difference of at least 20 days between the shortest and longest menstrual cycle. 

Irregular periods can also lead to problems when women are trying to get pregnant as it becomes difficult to accurately track ovulation, the time when they are most likely to conceive. 

The latest UK Government data indicates just over 48million people have received two doses of Covid vaccines. 


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