Some researchers recently said they believe there is a link between COVID-19 mRNA vaccines and a small number of people who develop myocarditis — inflammation of the heart muscle. Here are answers to some of the questions people ask:
What causes myocarditis?
“It’s not a very common thing,” said Dr. Caroline Quach Thanh, a pediatric infectious disease specialist and medical microbiologist at CHU Sainte-Justine in Montreal.
When myocarditis occurs, it often occurs after various types of viral infections, from the common cold to diseases of the gastrointestinal tract. The virus causes inflammation in the heart as part of the body’s immune response.
Often, myocarditis is not serious and goes away on its own after an injury.
Not much can be done, in many cases. “You have to wait for it to be over,” Quach Thanh said.
In the rare cases where inflammation affects the heart’s ability to pump blood, treatments can include anti-inflammatory medications or steroids.
What are the symptoms?
Some people don’t notice anything at all. But according to Dr. Peter Liu, cardiologist and chief scientific officer at the University of Ottawa Heart Institute, the most common symptoms include:
- A feeling of pressure in the chest that does not go away.
- Pain that gets worse when you take a deep breath.
- Shortness of breath.
- In more serious cases, arrhythmia and fainting.
Where does the vaccine link theory come from?
It has been difficult to determine whether the small number of people who developed myocarditis after receiving the Pfizer-BioNTech vaccine developed it anyway, or if it was caused by the vaccine.
Last week, the Israeli Ministry of Health announced that a study it conducted convinced them of a “possible link” between receiving the second dose of the vaccine and developing myocarditis. The studies so far have looked at the Pfizer vaccine but not the Moderna vaccine, which is also an mRNA injection.
Israeli officials said that of the more than five million people vaccinated, 275 cases of myocarditis were reported between December 2020 and May 2021 — mostly among men aged 16 to 30.
The Israeli government said hesitation was rare and most cases were mild.
Pfizer said it is aware of the Israeli findings, but does not believe a causal link has been established. The company said the rate of post-vaccination myocarditis was no higher than normal in the general population.
US health officials also monitor the frequency of myocarditis after vaccination.
Who is most affected?
Based on the studies done so far, it appears that adolescents and young adults are more likely to develop myocarditis after vaccination – although it is still a very rare development in this group.
This is consistent with myocarditis in general, Liu said. He said that males are more likely to have the condition than females, regardless of the cause, and they are usually young.
Why the vaccine may lead to myocarditis?
Currently available mRNA vaccines, including Pfizer-BioNTech, elicit a strong immune response”, which is why they are so protective. [against COVID-19]Liu said.
In addition, younger people tend to have stronger immune responses and when they get their second vaccine dose, their immune systems are already ready from the first.
In rare cases, he said, an “overactive” immune response can occur, leading to inflammation around the heart.
Do Canadians get myocarditis after vaccination?
Public Health Canada and Health Canada say they’re close Myocarditis monitoring reports, but we have not yet seen a clear association with mRNA vaccines.
“Canada is not seeing higher rates than would be expected in the general population (outside of the vaccine context),” a spokesperson for both agencies said in an email to CBC News.
Cardiologist Liu said the information he’s seen so far indicates that myocarditis caused by the mRNA vaccine does occur, but rarely.
Plus, it doesn’t seem to happen until after the second dose, he said.
Liu said Israel is likely to see more cases of myocarditis after the vaccine, because it is far ahead of Canada in giving people second doses of the vaccine.
Watch | Second dose switch against delta variable:
Quach Thanh said this is an advantage for Canada in terms of monitoring vaccine side effects.
Because myocarditis is more common in young people, by the time it’s their turn for a second dose, there should be clearer data from other countries, including the United States, on how much of the link actually exists, she said.
So should anyone avoid vaccinations?
The overwhelming consensus among experts – including those in Israel who have vehemently stated that there is a link to myocarditis – is not at all.
“The effectiveness of the vaccine outweighs the risks,” Nahman Asch, the country’s epidemiological response coordinator, told an Israeli radio station.
Canadian experts agree, pointing out that COVID-19 is itself a serious threat to heart health — so getting an effective vaccine to prevent it is the right thing to do.
I suffer from heart disease. Should I get the vaccine?
The Heart and Stroke Foundation says it’s especially important for people with cardiovascular disease to get vaccinated to protect themselves from COVID-19.
“You’re worse off if you get COVID,” said Patrice Lindsey, director of health systems change at Heart and Stroke Foundation of Canada, noting that the organization has not seen any potential vaccine side effects so far that would justify not infecting someone. vaccination.
“The risk of rare cases of myocarditis occurs mostly in younger individuals, without prior heart conditions, and is usually self-curing,” he said.
“Patients with heart disease are not at greater risk.”
So what is the bottom line?
All the experts CBC News spoke with emphasized that Canadians – including teens and young adults – can feel confident that COVID-19 vaccines are safe and effective.
But they said it is still important for the public and health care providers to be aware of the potential risks of carditis after the second dose of Pfizer-BioNTech.
This way, if someone develops symptoms and recently received their second dose of the vaccine, they will not just ignore the symptoms and should speak to their healthcare provider. In turn, this information can help health care providers diagnose myocarditis more quickly and determine whether or not any treatment is needed.