Periods, Pregnancy, and COVID Vaccination

Periods, Pregnancy, and COVID Vaccination

Nations around the world are running COVID-19 vaccination programmes to bring us through the pandemic. A whopping 5.4 BILLION doses have been administered already according to Our World in Data. There have been some questions about the COVID vaccine and how it affects the menstrual cycle (your period), and concern about whether or not they are safe in pregnancy. This article will round up what we know so far, so you can stay informed.

Why the COVID vaccine might affect your period

The COVID vaccine stimulates your immune system to create antibodies against the COVID-19 virus. The molecular messengers used to build up your immune system are similar to those involved in the menstrual cycle, particularly ones called cytokines. They have a role in the cramping pain and discomfort you might feel just before your period.

This explanation could be why some women reported worse period cramps after being vaccinated. Cytokines are also present in the uterus (womb) lining – this is what is shed when you bleed during your period. This means that this cytokine explanation could also be why some women report heavier bleeding temporarily after being vaccinated.

Does the COVID vaccine affect periods?

Research is still underway to determine the effect of the COVID vaccine on menstruation. The MHRA (the organisation ensuring vaccine safety in the UK) shared that as of May 2021 they had received 4000 reports of ‘period problems’ following vaccination including heavier periods and missed periods. One study found that 0.5% of menstruating women who received the vaccine and used their app reported irregular periods after their vaccine.

Dr Emma Duncan from Kings College London reassured that this rate is “still very low” and highlighted that irregular periods can have many causes.

The MHRA are “closely monitoring” the data and stated that current evidence doesn’t suggest an increased risk of these problems with the vaccine.

Woman on couch with period pain
Image credit:  Sora Shimazaki from Pexels

If your period is affected, it won’t be for long

Dr Victoria Male is a Reproductive Immunologist at Imperial College London. She stated that fortunately almost all the reports of period issues resolved within one cycle, sometimes two. Gladly, these effects are temporary and are “short term changes”.

However, it is important to note that that we do not yet have enough data to determine if these effects were caused by the vaccine, or how common they are.

These effects can be managed relatively easily

Dr Duncan advises that simple ibuprofen and aspirin can help to deal with these effects if you experience them. These medications can ease pain as well as having a small effect on menstrual flow. This means they can reduce how much blood you lose. These effects should be temporary, but if they continue beyond one or two cycles or become severe, it’s best to see your doctor.

The COVID vaccine and pregnancy

Pregnant woman hands on stomach
Image credit: SHVETS production from Pexels

It is important for pregnant women to consider COVID-19 vaccination as they have a higher risk of premature labour and needing intensive care admission, although the overall risk of getting the disease is low. There is also emerging evidence that symptoms can last longer, possibly resulting in an increased risk of long COVID.

The Joint Committee on Vaccination and Immunisation (JCVI) advises health departments in the UK on vaccination. Their current guidance states that pregnant women should be offered the vaccine alongside the rest of the population, as does the WHO and the CDC. Pfizer and Moderna are preferred as more data is available – 90,000 pregnant women in the US have been vaccinated with no safety concerns.

There is also no need to avoid trying for a baby after your vaccine, as there is no evidence to suggest it affects your fertility.

The WHO as well as regulatory bodies in the US, UK, Canada and across Europe are constantly reviewing the available evidence on the vaccines. Reassuringly, there is none so far that identifies a risk to pregnancy or fertility and further studies are underway.

Please do check the latest information where you are, as it often changes in response to the latest research.


Which COVID vaccine is best?

All COVID vaccines train your immune system to fight against the virus when it enters your body. Each works in a different way and some have different dosage schedules. They also have different side effect profiles and are approved for different population groups; for example some are only licensed for adults. This information can change as we find out more and as countries go through their rigorous approval processes.

As knowledge grows and as there are many different factors to consider, it is hard to directly compare the vaccines. We do know for a fact that two doses provide better protection than one. This benefit of full vaccination has been shown to be even more important for the Delta variant. We also know that being fully vaccinated reduces your chance of hospitalisation or dying from COVID-19 infection, and reduces its spread. Your local COVID vaccination provider can determine which vaccine is suitable depending on your age, allergies, and medical issues.

How long after a COVID vaccine can you have a reaction?

Reactions can occur from a few hours after the vaccine being given. Most are mild and and only last a few days at most, such as a sore arm at the injection side, feeling achey, feeling tired and having a mild headache. Sometimes people feel feverish and get chills, but this is easily relieved with simple paracetamol as per NHS advice.

Are COVID vaccines FDA approved?

The US Food & Drug Administration is responsible for ensuring the safety of medicines and medicinal products, including vaccines. Full FDA approval is granted when enough data demonstrates that a vaccine is safe and effective. It also involves examining and approving the manufacturing facilities and process. This requires vast amounts of time and resource, when the need to protect people against COVID rapidly became an emergency.

To respond to the emergency quicker, the FDA used it’s Emergency Use Authorisation process. This allowed them to prioritise COVID vaccines and analyse large amounts of data to determine the benefits more rapidly. EUA was granted for Pfizer, AstraZeneca/Oxford, Moderna, and Johnson & Johnson vaccines for example. The Pfizer vaccine has recently been granted full FDA approval.

Are COVID vaccines free?

This depends on the country in which you live, although most countries provide them for free. They are free in the UK, USA, Germany, France, Australia and China for example. However, there are accounts of providers in some countries charging its citizens, as well as numerous scams tricking people into giving them money for a vaccine. It’s best to check official governmental information for clarity where you are.



Stef is a medical doctor and public health specialist, with a passion for the prevention of illness. When she isn't working at her day job or trying to keep her plants alive, she often has her nose in a book or goes for a walk with an audiobook for company.

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