A new study has confirmed a link between the Covid-19 vaccine and periods

Since the rollout of the Coronavirus vaccine in the UK, many people have shown concerns about the jab’s impact on their period. In fact, 30,000 people have reported period irregularities after getting the vaccine, as per the MHRA Yellow Card scheme, including bleeding earlier than expected (often shortly after the vaccine), spotting, heavier bleeds or painful periods.

However, a new study funded by the National Institute of Health (NIH), has found that the Covid-19 vaccine was associated with a less than one-day change in menstrual cycle length for both vaccine-dose cycles, compared with pre-vaccine cycles.

The International Federation of Gynecology and Obstetrics classifies a variation in cycle length as normal if less than 8 days. Diana W. Bianchi, M.D., director of Eunice Kennedy Shriver National Institute of Child Health and Human Development, said: “It is reassuring that the study found only a small, temporary menstrual change in women.

“These results provide, for the first time, an opportunity to counsel women about what to expect from COVID-19 vaccination so they can plan accordingly.”

However, the study noted that questions still remain about other possible changes in menstrual cycles, such as “menstrual symptoms, unscheduled bleeding, and changes in the quality and quantity of menstrual bleeding.”

Reproductive immunologist Dr. Victoria Male of Imperial College London, has previously called for “robust research” into menstrual changes after Covid-19 vaccinations, writing in the BMJ:

 “Vaccine hesitancy among young women is largely driven by false claims that Covid-19 vaccines could harm their chances of future pregnancy. 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.”

Here, Dr. Male answers our questions about the effect the vaccine could have on your menstrual cycle…

What sort of changes to their menstrual cycle have women reported following the Covid vaccine?

The reports have been quite varied. Some people have reported heavier periods; some lighter. Some people have reported earlier periods; and some later. Some people have even reported missed periods. This variation in the reports is one of the reasons it’s been difficult to determine whether these changes are definitely linked with the vaccine.

Another is that we also have to take into account variations in the menstrual cycle that happen anyway. But work is being done to determine whether this is a side-effect of vaccination. If nothing else, it means we will be able to warn people that they might expect these changes, in the same way that we currently tell them that they might expect a sore arm or a bit of a temperature.

Why are people noticing these changes?

Research is being done on this. First, it will tell us if this is a common side effect, and how common it is. Second, the kinds of situations in which this occurs might give us some clues as to the potential mechanism. We know that the immune system affects sex hormones, and sex hormones affect the immune system, so if this is a real effect, I think it is likely that it is being mediated by changes to the ratio of oestrogen and progesterone during the menstrual cycle.