Myocarditis and Covid-19 vaccines: should you be worried?
We look at the link between myocarditis and Covid-19 vaccines, including which age groups are at a higher risk.
Updated 21 June 2023
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Does the Covid-19 vaccine cause myocarditis (heart inflammation)?
There have been rare cases of myocarditis (inflammation of the heart muscle) following the Moderna and the Pfizer vaccine in the UK, and it has been listed as a very rare side effect.
Myocarditis has also been listed as a rare possible side effect of the Novavax vaccine, after a very small number of cases were reported during clinical trials.
For every million doses given of the monovalent Pfizer/BioNTech vaccine, there have been 10 reports of myocarditis and 6 reports of pericarditis, according to the Medicines and Healthcare products Regulatory Agency (as of 23 November 2022). There have been 14 reports of myocarditis and 8 reports of pericarditis for every million doses given of the monovalent Moderna vaccine over the same period.
While reports of myocarditis following any Covid-19 vaccine are rare, cases are more common in young males aged 18 to 29 years following the second dose. Most people who have been affected have experienced a mild illness and recovered without medical treatment.
Myocarditis can cause heart scarring that can be detected with cardiac MRI – there is a small chance of scarring causing a life-threatening arrhythmia in the future, and therefore people who are affected are likely to be offered long-term follow-up and monitoring.
Research has found that Covid-19 itself is much more likely to cause myocarditis than the vaccine is, and people who are vaccinated have a much lower risk of getting other serious complications caused by Covid-19.
Who is at highest risk of myocarditis following the vaccine?
The risk of getting myocarditis or pericarditis after the vaccine is very low.
In the UK, reports of myocarditis following the vaccine have been highest in the 18-29-year-old age groups, following a second dose of the vaccine. Men are generally at higher risk of myocarditis than women, whether or not it is linked to the vaccine.
Is there a risk of cardiac arrest from the Covid vaccine?
No. There is no evidence that people are at an increased risk of cardiac arrest in the days or weeks following the Covid-19 vaccine.
What research is being carried out?
Because myocarditis linked with Covid vaccines is a recent and rare issue, there are still many unanswered questions, including what the possible long-term effects might be.
Researchers supported by the BHF, including researchers from the BHF Data Science Centre, are continuing to look into myocarditis caused by both Covid-19 and the vaccine. For example:
- A project co-led by Professor John Greenwood is looking to understand the extent of heart muscle damage in patients who are hospitalised with Covid, and how well they have recovered after six months.
- A large UK study involving BHF researchers, published in August 2022, found that the risk of myocarditis is much higher following Covid-19 infection than in the weeks following vaccination.
- A study by researchers at the BHF Cardiovascular Research Centre in Glasgow, published in May 2022, found that 1 in 8 people who were hospitalised with Covid-19 were later diagnosed with myocarditis. The study also showed that in addition to heart inflammation, severe Covid can cause inflammation across the body and damage to the kidneys.
Learn more about key Covid-19 research projects that the BHF is supporting.
Do other vaccines carry a risk of myocarditis?
Research published in The Lancet medical journal in April 2022 shows that there is no greater risk of developing heart inflammation after a Covid-19 vaccine than after other common vaccines, including the flu jab.
Researchers from Singapore looked at the findings of 22 different studies, covering 405 million doses of different vaccines around the world – including flu, smallpox, polio, measles, mumps and rubella. Overall the rates of myocarditis and pericarditis following Covid vaccines weren’t significantly different to other vaccines, including flu, although rates of myocarditis or pericarditis in young men were higher following mRNA-based Covid vaccines such as Moderna or Pfizer.
The researchers, writing in The Lancet medical journal, suggested that the rare cases of post-vaccine myocarditis and pericarditis might be connected to the overall immune response to vaccination, not specifically because of the Covid-19 vaccination or the spike protein it is based on. They suggested that the reports of myocarditis and pericarditis might be because of the large scale of Covid-19 vaccination and the close scrutiny it has had.
Based on these findings, the researchers said that the benefits of Covid-19 vaccines (including a reduced risk of severe illness or death) far outweigh the very small risk of myocarditis or pericarditis, which is also seen for other vaccines.
Are children at higher risk of heart inflammation from the vaccine?
Cases of heart inflammation (myocarditis or pericarditis) after the vaccine in children and young people are rare. Overall the rate is lower in children than in adults aged 18-39.
The independent Medicines and Healthcare products Regulatory Agency (MHRA) has reviewed all the evidence and confirmed the Pfizer vaccine is safe and effective for children aged 5 and over. This followed an extensive review of the safety, quality and effectiveness of the vaccine in this age group.
What is myocarditis? What is pericarditis?
Myocarditis means that your heart muscle is inflamed. It usually happens after catching a virus. It can be mild or serious. In serious cases it can cause abnormal heart rhythms, or make it more difficult for your heart to pump blood.
Most people who get acute myocarditis make a good recovery and don't have long-term problems. In some cases, myocarditis can result in long-term damage to the pumping function of the heart (heart failure). Myocarditis, which is most commonly triggered by an infection, can also lead to scarring of the heart tissue, which in some cases could cause heart rhythm disturbance later in life.
Pericarditis is inflammation of the lining around the heart, whereas myocarditis is inflammation of the heart muscle. Myocarditis can often happen together with pericarditis, and they can have similar effects, which is why they are often linked together in vaccine incident reporting.
What are the symptoms of myocarditis after the vaccine?
Symptoms of myocarditis linked to the vaccine generally appear within a week of a vaccination. If you get any of these new symptoms, you should seek medical help, especially if these symptoms don’t go away.
- Pain or tightness in the chest, which may spread across the body
- Pain in the neck that may spread across the shoulders and/or arms
- Shortness of breath when walking or doing gentle exercise
- Difficulty breathing when resting, or feeling light-headed
- Feeling palpitations (like your heart is fluttering, or racing or pounding, or beating with an unusual rhythm)
- Feeling like you need to be sick.
They may not mean you have myocarditis, but they are signs you should get medical help, whether or not you have recently been vaccinated.
Can the vaccine cause changes to your heartbeat?
Some people have reported feeling a faster heartbeat in the days after their Covid-19 vaccine. This can be part of your body’s normal immune response to the vaccine and is not normally a cause for concern.
It can be difficult to tell the difference between a faster heartbeat which may not be anything to worry about, and one which needs medical help. It can be a symptom of myocarditis which, though rare, needs medical attention. So if you get new symptoms such as chest pain, shortness of breath or feelings of having a fast-beating, fluttering, or pounding heart, you should seek medical help, especially if these symptoms don’t go away.