Teens are six times more likely to develop heart inflammation from contracting SARS-CoV-2, the virus that causes COVID-19, than as a result of the Pfizer vaccine. (Envato)
  • Viruses like SARS-CoV-2, which causes COVID-19, can cause heart inflammation. This condition is also an extremely rare side effect of Pfizer’s COVID vaccine.
  • The chances of developing the heart condition after being vaccinated with Pfizer’s COVID jab are higher in teen boys who have received two shots, but most cases are mild and nearly all people make a full recovery in a few days.
  • Common symptoms to look out for post-vaccination are chest pain, trouble breathing or an irregular heartbeat. If you’re concerned, seek medical care.
  • The possible organ damage that can be caused by COVID-19 as a result of heart inflammation is far more severe than the small risk associated with the vaccine.

Scenario: You have a child between the ages of 12 and 17 who is now able to get vaccinated with one shot of Pfizer’s COVID vaccine. But you’re wondering why your teen will only get one — instead of two — jabs like you had.

“Did the health department decide to cut the dose in half because the risk of serious side effects for my child is dangerously high?” you ask yourself. And, you ponder, “Is the shot worth the risk?”

The side effect in question: Myocarditis, commonly known as heart inflammation, which, up until now, has occurred more frequently in teen boys than girls

We’ve combed through the studies and data and have broken down the science, risks and reasons for teen vaccinations in an easy-to-understand way, so you can make an informed choice about your teen’s jab. 

In short: Teens are six times more likely to develop heart inflammation from contracting SARS-CoV-2, the virus that causes COVID-19, than as a result of the Pfizer vaccine. This is based on United States data published in a preprint study (which hasn’t been peer-reviewed) in July. 


By 14 November, 241 661 teenagers, or 4.5% of the 12 – 17 years population of about 6.5-million, had come forward to get their jabs.

What is heart inflammation?

Your heart is made of three different muscles: myocardium, pericardium and endocardium.

The myocardium is the middle layer of your heart and also the biggest. It is in charge of pumping your heart.

There’s a protective layer on the outside of the heart muscle called the pericardium. This tissue helps to protect your heart from infection, and it also keeps it in place in your chest.

Finally, the endocardium on the inside of the heart muscle helps to keep the blood inside the heart’s chambers separate from the blood that’s fuelling the function of the heart muscle itself. 

When any of these three muscles become infected, they become inflamed as a result of the infection. Inflammation is your body’s immune system’s response to an irritant. The ensuing condition is called myocarditis, pericarditis or endocarditis. 

This infection is most commonly caused by viruses, but bacteria, fungi and medicines can also lead to these conditions. 
SARS-CoV-2 is a virus that can cause myocarditis or pericarditis. But these conditions are also rare side effects of the Pfizer COVID vaccine.

How serious is heart inflammation?

Myocarditis normally resolves on its own, so although having your heart muscle inflamed sounds scary, people generally recover without treatment or lasting damage.

But in some cases, heart inflammation symptoms can be more severe — especially if left untreated.

Here’s why.

Once a germ such as a virus has entered the cells in your heart tissue, your immune system will jump in to eradicate the virus, and in doing so it will also damage your own cells. 

This may cause damage to the heart muscle and affect whether your heart beats at its usual pace. Any change to your heartbeat, either faster or slower, is bad.

Because SARS-CoV-2 infection can lead to myocarditis or pericarditis, this risk exists in people who get infected by the virus and develop COVID-19. There is evidence that shows people with COVID sometimes have permanent damage to their heart, lungs, and potentially even their brain.

In extreme cases, severe damage can lead to heart failure if the muscle is no longer able to pump blood around your body.

When your blood stops pumping, it can collect in your heart and form clots. These clots can block the blood vessels in the muscle causing a heart attack or travel to your brain and cause a stroke.

So what about Pfizer’s COVID vaccine — how does that lead to myocarditis and is it mild or severe heart inflammation that is associated with it?

Vaccines trigger the same immune response to fight off a harmless version of the virus as the reaction your body would have when it’s infected by the actual virus. Because of this, people may experience common infection symptoms, like fever, after they’ve been vaccinated.

In the case of other medications that can lead to myocarditis, such as antibiotics or cancer drugs, this sometimes happens because of allergic or toxic reactions to the medicine. It’s still too early to say the exact cause of these vaccine-related myocarditis cases, but a similar trend was seen previously with the smallpox vaccine

The condition seems to be happening more frequently in boys between the ages of 12 and 17 after receiving their second dose of Pfizer’s jab. 

Symptoms tend to appear within the first three days post-vaccination, with most people recovering within a few days without having to receive treatment or go to the hospital.

Because myocarditis and pericarditis are far more common after a second than a first shot of Pfizer’s jab, South Africa is currently recommending that children under 18 only get the first shot  — until more data becomes available as Pfizer’s vaccine is being rolled out among teens around the world.

What is the risk of your child getting heart inflammation after vaccination?

In short: Heart inflammation after one jab of Pfizer is extremely rare.

Side effects are classed by how often they occur. More common side effects, such as arm pain, also tend to be more mild.

A side effect that occurs in one in every 10 people is considered very common. Rare side effects are seen in between one in every 10 000 to one in every 1 000 vaccinated people.

An extremely rare side effect happens in less than one person for every 10 000 people immunised. This translates to fewer than 0.01% of those who get the jab.

Heart inflammation as a COVID vaccine-related side effect falls into the extremely rare category.

August data from the US government’s Centres for Disease Control found that there were fewer than three reports of heart inflammation for every million people between the ages of 12 and 15 years who received their first Pfizer shot. But this rose to almost 21 reports after the second dose.

Those at highest risk are boys aged 16 to 17 —  there were almost 72 cases per million people fully immunised with Pfizer in this age group who developed myocarditis or pericarditis as a vaccine-related side effect. But even then, heart inflammation is still considered an extremely rare side effect as it occurs in fewer than 0.01% of 16- to 17-year-old boys.

The occurrence of myocarditis after one Pfizer shot was significantly lower than after two doses:  boys in this age group were almost 14 times more likely to develop the condition after two doses.

If you’re just going by the numbers, however, the chances of heart damage from having COVID-19 are considerably higher than those associated with vaccination.

Research from early COVID cases found that seven to 20% of patients who developed myocarditis as a result of COVID, had damage to their hearts. A 2020 paper in the journal Nature Public Health Emergency Collection found that 44% of COVID patients with myocarditis in Wuhan, China developed an irregular heartbeat which could potentially lead their hearts to stop pumping or result in a stroke. 

Patients who developed heart problems after being infected with SARS-CoV-2 were also more likely to fall seriously ill needing hospitalisation and had a higher chance of dying than those who developed heart inflammation as a result of vaccination.

Moreover, just over 30% of COVID patients in a United Kingdom study suffered from heart damage and two out of three had problems with at least one organ, according to a November 2020 BMJ paper.

Given the high risk of long-term heart damage, as well as the possible harm to other organs, brought on by both severe and mild COVID cases, science, so far, therefore shows us that it’s much safer and more worthwhile to get a COVID vaccine than not having one and risk getting COVID as an unvaccinated person.

Why?

Because we know that COVID jabs hugely reduce the possibility of falling seriously ill with COVID (that includes developing serious myocarditis or pericarditis) and it also makes us less likely to contract SARS-CoV-2.

Why are teens being vaxxed at all?

Teens are far less likely than adults, particularly those older than 50, to fall seriously ill with COVID. So why should they get vaccinated if COVID normally doesn’t do much to them? 

There are three reasons, according to Refiloe Masekela, who heads up the department of paediatrics and child health at the University of KwaZulu-Natal, in Durban. She was speaking during a Discovery Health webinar on COVID-19 vaccines in November.

Firstly, South African family structures are different from families in, for instance, Western countries. “We have many blended, multi-generational families where adolescents can spread the virus to people who are more likely to get very ill [for example, grandparents], even if they don’t get that sick themselves,” explained Masekela.  

[WATCH] Is one better than none? Why SA’s teens are only getting half a COVID jab

Secondly, vaccinating teens will allow this group to socialise with their friends much more safely, and their education can continue uninterrupted. 

Lastly, Masekela says, teenagers aren’t totally spared from a severe case of COVID. 

In South Africa, almost 12% of COVID cases occur among children younger than 19 — this age group accounts for around one in 20 hospital admissions in the country, August data from the National Institute for Communicable Diseases shows. 

What to look out for: signs and symptoms in kids

Because heart inflammation could potentially be triggered by a variety of causes, there is no set symptom list for everyone. Early on, some people may, for instance, not have any symptoms.

In a portion of people, however, the symptoms of heart inflammation may be similar to those of a heart attack, where they experience chest pain or they may have an irregular heartbeat, trouble breathing, chest pain and fever.

But many children may have a hard time telling you about their symptoms, so what can you do if you’re worried about your kid? 

Parents could consider discussing the side effects associated with the vaccine with teenagers before they get vaccinated, says Masekela.   

If your child is feeling unusually tired, they have pain in their chest and they’re feeling weak, Masekela says those things should trigger a visit to a doctor.

Or, instead, you can take precautions, Masekela explains: Don’t let your teen do sports or heavy exercise for four to five days after their vaccination. 

What is the treatment for heart inflammation?

People who have a mild case of myocarditis, for the most part, just need to rest. 

An October paper in the New England Journal of Medicine found 54 cases of myocarditis among 2.5-million people over 16 who got at least one dose of the Pfizer jab in Israel (most people were diagnosed with myocarditis after their second dose). Over three-quarters of these cases were mild and there was one case resulting in a heart attack.

Some patients with heart inflammation may require medication.

For example, steroids could help suppress the immune system to stop your body’s natural protective process from damaging the heart tissues, in other words, stop the inflammation.

If your doctor detects underlying heart conditions that are causing the problem, drugs will be prescribed to manage your symptoms. Blood pressure medication could, for instance, be prescribed to take pressure off your heart. Or, in cases where the heart inflammation is causing your heart to beat irregularly, doctors could also ask you to take medication that prevents blood clots. 

People who develop a severe case of myocarditis may need to be hospitalised. 

Once admitted these patients may need medication to be given into their veins to help support their heart. Very ill patients are sometimes put on heart machines that take over the function of their heart by removing carbon dioxide from their blood, or adding oxygen to it. 

In the most severe cases, a pacemaker (a small device to help control your heartbeat) may be implanted. 

A small proportion, between 0.5% and 4%, of people who develop myocarditis (these are not COVID-specific or COVID vaccine-related cases, but myocarditis cases in general) experience heart failure, which may require a transplant. This figure was calculated by reviewing all myocarditis research published globally between 1966 and 2010 for a Lancet study published in 2014.

The verdict? 

Overall, there is a very small chance of experiencing heart inflammation post-vaccination — and in rare cases where this occurs, most of the myocarditis-related cases are mild and people recover within a few days.

The earlier you get medical attention, the better your outcome is likely to be. So it’s better to go in aware of the risks and keep an eye out for any possible warning signs after getting your shot.

Heather Zar, who heads up the school of child and adolescent health at the University of Cape Town, concluded during the November Discovery Health webinar: “The very small risk shouldn’t deter parents from taking their teens to get vaccinated. We’ve seen what COVID has done to our education system and our economy. The vaccines will help us move to something closer to normal.”

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Aisha Abdool Karim is a senior health reporter at Bhekisisa.

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Joan van Dyk is a senior health journalist at Bhekisisa.