Myocarditis and Covid-19 vaccines: should you be worried?2023-02-24T16:54:38+00:00

Myocarditis and Covid-19 vaccines: should you be worried?


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 (even more rarely) Pfizer vaccines in the UK. 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.

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.

Research published in April 2022 suggests that overall, myocarditis is no more likely to be triggered by a Covid vaccine by than any other vaccine. It’s also worth noting 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.

What is the risk of getting myocarditis or pericarditis after the vaccine?

The risk of getting myocarditis or pericarditis after the vaccine is very low.

According to the MHRA Yellow Card report summary, published on 1 December 2022, even in the highest-risk age group (18-29), there were just 29 reports of suspected myocarditis or pericarditis for every million second doses of the monovalent Pfizer vaccine given in the UK up until 23 November 2022. The risk is even lower following a monovalent Pfizer booster, with just 17 reports per million people in this age group. In other age groups the risk is even lower.

For the monovalent Moderna vaccine, there were 70 cases of suspected myocarditis or pericarditis for every million second doses given in the UK, in this age group. As with the monovalent Pfizer vaccine, the risk is much lower after a booster, with just 20 reports per million monovalent Moderna boosters given (up until 23 November 2022). In other age groups the risk is even lower.

So far, the bivalent vaccine is following a similar pattern. The Yellow Card report summaryfrom 13 January 2023 reported that for the bivalent Pfizer vaccine, there were just 14 cases of myocarditis and pericarditis per million doses in the 30-39 age group (up until 28 December 2022). Currently, there isn’t enough data to estimate the risk to younger age groups or for the bivalent Moderna vaccine.

The World Health Organisation has reviewed data from 744,235 doses of the Novavax vaccine given in Australia, Canada, the European Union, New Zealand, and South Korea up until 30 April 2022. Amongst these recipients, there were four reports of myocarditis, 29 reports of pericarditis, and two reports of myopericarditis. More recent data from Australia (until 21 August 2022) showed seven cases of myocarditis and 26 cases of probable pericarditis after 209,000 doses of the Novavax Covid vaccine.

Serious illness with myocarditis after the vaccine has so far been exceptionally rare, although more research is being carried out into the long-term effects of post-vaccine myocarditis on heart health.

Do other vaccines carry the same risk?

Research published 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.

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 instance:

  • 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.

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.

Who is at risk from myocarditis following the vaccine?

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.

In the UK, up to 23 November 2022, there were 554 suspected cases of myocarditis or pericarditis reported in the 18 to 29 age group following the vaccine. This is an average rate of 31 reports per million doses.

In the 30 to 39 age group, there were 470 cases suspected cases of myocarditis or pericarditis reported in the same time period. This is an average rate of 27 reports per million doses.

Are children and young people 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.

In the UK, up to 23 November 2022, there were 83 cases of myocarditis or pericarditis reported in those under 18 following the vaccine. This is an average rate of 11 cases per million doses. Pfizer is the only vaccine recommended for under-18s.

Overall the rate is lower in children than in adults aged 18-39. There have been no reports of suspected myocarditis or pericarditis following booster doses in under 18s.

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.

As a precaution, the interval between doses is longer for children than for adults, in order to reduce the small risk of developing myocarditis linked to the vaccine. As well as this, if a child (who is not in an at-risk group) gets Covid after their first vaccine dose they should wait 12 weeks from their positive Covid-19 test to have their second jab. This is also to reduce the small risk of developing myocarditis linked to the vaccine.

Is there a risk of cardiac arrest from the Covid vaccine?

No. There is no evidence that people are at risk of cardiac arrest in the days or weeks following the vaccine.

Studies looking at myocarditis and pericarditis after the vaccine have not found any increased risk of death or cardiac arrest, compared with being unvaccinated. A large study of 4 million vaccinated people in Denmark, published in the BMJ in December 2021, found there were no deaths or diagnoses of heart failure in people who were diagnosed with myocarditis or pericarditis after being vaccinated.

In the UK, no figures have been published for cardiac arrests in under-18s following the vaccine, which suggests there have been too few reports to be published, or none at all.

Catching Covid-19, on the other hand, can significantly increase your risk of cardiac arrest and death.

Is there any link between the Covid-19 vaccine and cardiac arrests at football matches?

No, there isn’t. There have been a number of cardiac arrests at football matches in recent months, amongst fans and players. But there is no evidence for any link to the vaccine, despite some misleading reports on social media. We can’t even say for sure that there have been more cardiac arrests than usual. Research has showed that having previously had a coronavirus infection is much more likely than the Covid-19 vaccine to lead to heart problems – although these cardiac arrests may not be linked to coronavirus infection either.

These rumours began after Denmark’s Christian Eriksen suffered on-field cardiac arrest during Euro 2020 in the summer. Inter Milan have since confirmed that he had not yet been vaccinated at the time of his collapse.

An on-field collapse or cardiac arrest can be the first sign of a heart condition, and is not necessarily associated with myocarditis.

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.

Even though myocarditis cases after the vaccine have usually been mild, it’s still important to get medical help.

If you develop myocarditis you should have a blood test which is sent to specialist virologists in London. This will help researchers to understand how myocarditis develops and whether further vaccines are recommended for you. You should also be referred for a cardiac MRI scan. This will be to check whether there are any changes to your heart function and look for any evidence of inflammation or scarring in the heart.

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.

I’ve heard about people getting myocarditis after the vaccine and I’m worried. Should I have my second dose/booster dose?

Yes. It’s recommended that you have your second dose (or booster dose), if you are eligible. Although some cases of myocarditis have been linked to the vaccine, in these cases the illness has generally been mild, and those affected have mostly felt better quickly, following treatments and rest. Scientists have also worked hard to time the doses to maximise your protection against Covid-19 while minimising your risk of myocarditis.

I was diagnosed with myocarditis after having the vaccine. Should I have another dose?

No, you should get advice from your health professional if you were unlucky enough to be one of the few people who have been diagnosed with myocarditis due to the vaccine. You should be asked for a blood sample to test your levels of antibodies. This will help understand how much you are likely to benefit from further vaccine doses and will be used to inform advice on whether you should have another vaccine dose.

I’ve had myocarditis or pericarditis in the past, should I have a Covid vaccine?

Yes. Having had myocarditis or pericarditis (unrelated to the vaccine) doesn’t mean you can’t have the Covid vaccine. There is currently no evidence that people with a history of myocarditis or pericarditis are at increased risk of developing it following the Covid vaccine. If in doubt, ask your health professional for advice.

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