- The heart has played a central role in COVID-19 since the beginning.
- Perhaps the most common point of conflict concerning COVID-19 vaccines is the risk of myocarditis following immunization, particularly among young people.
- Rates are highest in males between 18 and 30 years old.
- Based on a study out of Israel, the risk of post-vaccine myocarditis is 2.13 cases per 100,000 vaccinated, which is within the range usually seen in the general population.
Since the inception of COVID-19, the heart has played a crucial role. Cardiovascular disease is one of the leading causes of hospitalisation as reported by The Conversation.
Signs of heart damage
A significant number of patients hospitalized with SARS-CoV-2 infections have signs of heart damage, and many recover from infection with lasting cardiovascular injury.
It’s not surprising that debates over COVID-19 vaccines frequently centre around issues involving cardiovascular health.
The high-profile collapse of Danish soccer player Christian Eriksen in June initiated a myth about the link between sudden cardiac death and vaccination among athletes that persists several months later.
Perhaps the most common point of conflict concerning COVID-19 vaccines is the risk of myocarditis following immunization, particularly among young people.
What is myocarditis?
Myocarditis is an inflammation of the heart muscle most commonly caused by virus-like influenza, coxsackie, hepatitis or herpes.
Other causes include bacteria, fungi, toxins, chemotherapy and autoimmune conditions.
Some viruses infect heart muscle and cause direct injury to the heart, while others cause heart damage indirectly through the immune system.
Activation of the immune system in response to infection triggers the release of chemicals in the body called cytokines, which help clear infections.
In some cases, the levels of cytokines rise to unusually high levels to produce a “cytokine storm” that causes damage to the heart muscle.
Myocarditis by the numbers
Before COVID-19 the incidence of myocarditis was between one and 10 cases per 100,000 people per year.
Rates are highest in males between 18 and 30 years old.
Interestingly, most cases of myocarditis in the highest risk group are in otherwise healthy and active people.
The risk is higher for males, older adults (ages 50+) and children under 16 years old.
Soccer player Alphonso Davies, 21, of Canada’s national men’s team, was sidelined by heart inflammation after having COVID-19.
Post-vaccination myocarditis
Myocarditis following COVID-19 vaccination is rare and the risk is much smaller than the risks of cardiac injury linked to COVID-19 itself.
Based on a study out of Israel, the risk of post-vaccine myocarditis is 2.13 cases per 100,000 vaccinated, which is within the range usually seen in the general population.
This study is consistent with others in the United States and Israel which put the overall incidence of post-vaccine myocarditis between 0.3 and five cases per 100,000 people.
The kids are alright
The highest incidence of myocarditis after vaccination with mRNA vaccines has occurred within three to four days after the second vaccination in males who are under age 30.
In pediatric data, the median age is 15.8 years, with most patients being male (90.6%) and white (66.2%) or Hispanic (20.9%).
Reliable data on booster shots in this age group is not yet available.
Most studies show a clear benefit of COVID-19 mRNA vaccination with respect to myocarditis.
Only one study by Martina Patone, from the University of Oxford, and colleagues found more ambiguous results for those under 40 years of age based on myocarditis rates alone.
Repairing the damage
The treatment for myocarditis varies depending on its severity.
Adults with mild forms of myocarditis typically need only rest and non-steroidal anti-inflammatory drugs (NSAIDS) like ibuprofen.
More severe cases require medications or even mechanical circulatory supports like left ventricular assist devices to support heart function.
In some cases when treatment is no longer effective, a heart transplant is required.
In a multicentre series of patients under 21 years old, those with mild symptoms received only NSAIDs or no anti-inflammatory therapy at all.
How serious is it?
Over 80% of myocarditis cases not related to COVID-19 or COVID-19 vaccination resolve spontaneously. While 5% of patients die or require a heart transplant within one year of diagnosis.
Adults who develop myocarditis from COVID-19 have poorer outcomes than non-myocarditis COVID-19 cases. That also includes a higher risk of death.
In cases of myocarditis following COVID-19 vaccination, the vast majority of cases are mild and resolve quickly.
In adults, 95% of cases were deemed to be mild.
All children who had heart weakness had complete normalization of their heart function on follow-up.
Take-home message
The dynamic changes combined with rapid developments in research, make it challenging for the public to take in all the information about the risks and benefits of COVID-19 vaccines.
In cases like this, it is useful to turn to the guidance of medical organizations whose mandates are to protect the health and welfare of society.
Considering all of the available research, organizations including the American Heart Association, Canadian Cardiovascular Society, Heart and Stroke Foundation of Canada, Canadian Paediatric Society and the American Academy of Pediatrics encourage all who are eligible to be vaccinated against COVID-19.
That’s a message we should all take to heart.
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Source: The Conversation
