Pfizer and Moderna have launched trials to determine if there are long-term adverse health effects associated with their Covid vaccines.
The studies include monitoring the small number of Americans who experienced rare side effects after receiving the shots over the past two years.
Both companies must complete this long-term research from the Food and Drug Administration (FDA) as a condition of approval earlier this year.
Inflammation of the heart was the most common serious side effect reported from vaccinations – although it is still very rare.
A study by the British Columbia Center for Disease Control in Canada found that 58 out of a million recipients of Moderna’s two-shot vaccine developed the disease.
The same study found that 21 out of every million recipients of the original two-dose Pfizer vaccine also had heart problems.
Cases were most common in men under the age of 30, affecting more than 250 out of every million men aged 18 to 29.
The Centers for Disease Control and Prevention (CDC) said it has registered around 1,000 cases of heart disease in under-18s who have received Covid vaccinations.
While these cases usually resolve on their own without medical intervention, some worry that long-term heart damage could result.
A recent Canadian study found that 58 out of every million recipients of the Moderna COVID-19 vaccine developed heart inflammation. For Pfizer’s jab, the rate was 21 per million
Younger men are most likely to develop heart inflammation as a result of the COVID-19 vaccination. The Canadian study found that out of 1 million male recipients of the Moderna shot between the ages of 18 and 29, more than 250 developed a heart problem.
Da’Vion Miller (left), 22, of Detroit, Michigan, suffered myocarditis after receiving an injection of Pfizer’s COVID-19 vaccine. Isaiah Harris (right), 18, of Springfield, Arkansas, suffered a heart attack as a result of myocarditis. He had only been vaccinated the day before.
Cambridge, Massachusetts-based Moderna has already started two studies tracking the adverse effects of his shot, the latest in September.
New York City-based Pfizer told NBC that in the coming months it will start a study involving 500 teenagers and young adults under the age of 21.
The companies will follow some patients for up to five years, but results are expected to be available as early as next year, NBC reports.
Both companies used mRNA technology to develop their shots.
Myocarditis: A potentially fatal condition associated with COVID-19 and the flu
Myocarditis is a relatively rare condition that occurs when a person’s myocardium — the middle layer of their heart — becomes inflamed.
It’s usually a mild condition that resolves within weeks without medical intervention.
In some cases, it can lead to a stroke, heart attack, heart failure, or even death.
The condition can affect how a person’s heart pumps blood around the body.
It is a known side effect of some viral diseases, such as the common flu and COVID-19.
In rare cases, myocarditis can also occur after vaccination against a viral disease.
It is believed to affect fewer than 200,000 Americans each year, and deaths are rare when a person seeks medical attention.
Source: American Heart Association
While mRNA has existed for decades, the Covid vaccines were the first to use the technology to develop a medical product used at this scale.
Experts believe mRNA is perfectly safe to use, although the small precedent in its use for other drugs has many Americans concerned about the injections.
Billions of doses of mRNA vaccines have now been administered worldwide with very few side effects reported.
Myocarditis – inflammation of the heart muscle – is the most commonly reported serious vaccine-related side effect.
The condition occurs when the middle layer of the heart wall becomes inflamed.
Sufferers may experience shortness of breath, fatigue, and chest pain, among other symptoms.
It usually goes away on its own, but in rare cases it can lead to a heart attack, stroke, or even death.
Pericarditis occurs when the pericardium, the outer layer of heart tissue, becomes swollen.
It has similar symptoms to myocarditis and is also a relatively mild condition that often resolves on its own.
Both conditions are known to occur in people who have recently contracted a viral infection such as Covid or the flu.
Some studies suggest that Covid is significantly more likely to cause myocarditis than the vaccines themselves.
A study published last week in the Journal of the American College of Cardiology found rates of post-vaccination disease were highest in younger people.
Concern for young people – who are less likely to get severe Covid – has led some countries to restrict vaccination for certain age groups.
Denmark and Norway have already banned Covid vaccines for non-seniors, while Sweden has stopped recommending them for 12-17 year olds.
Da’Vion Miller, 29, of Detroit, Michigan, suffered from fatigue, shortness of breath and dizziness two days after receiving the first dose of Pfizer’s vaccine last October.
He was taken to the hospital where he was diagnosed with both myocarditis and pericarditis.
Doctors advised Mr Miller against receiving a second dose of the Covid vaccine, NBC reports.
Isaiah Harris, then 18, of Springfield, Arkansas, also suffered a case of vaccine-induced myocarditis last year.
He told 4029 News, ‘I was actually driving down the freeway and all of a sudden my heart rate went up a lot and it felt like it was pounding out of my chest… I woke up the next morning and I could hardly breathe.’
The teenager was taken to a local emergency room, where doctors determined he suffered a heart attack caused by myocarditis.
Just a day earlier, he had received a second dose of Pfizer’s COVID-19 vaccine.
A report released in February this year also linked the deaths of two teenagers, one in Connecticut and one from Michigan, to the Pfizer COVID-19 vaccine.
The couple each died within a week of receiving the injection.
Scientists determined they suffered from toxic cardiomyopathy caused by an immune response to the vaccine.
The condition occurs when a person’s heart muscle can no longer properly pump blood around the body.
Florida Surgeon General Dr. Joseph Ladapo, recommended last month that people under 40 should be banned from injecting.
However, the research paper he used to justify the move has been widely denounced by scholars as flawed.
The long-term safety studies being conducted by Moderna and Pfizer will be the first to determine the true risk of receiving the mRNA COVID-19 vaccines.
The shots were a novel product first available with an emergency approval in late 2020.
While the companies went through rigorous testing to get their vaccines approved, long-term data are not yet available as the earliest recipients are only two years away from being vaccinated.