Usually this blog deals with COVID-19 related subjects that have been in the recent news. This piece is a little different in that it aims to pre-empt news which will probably run within the next week or two.
Until now the AstraZeneca vaccine has been the main focus of media outlets who have run somewhat sensationalist headlines about its clotting risk which have in turn caused many to refuse vaccination. No drug, vaccine or procedure is entirely risk free - it is the balance of risk that matters; if I have a 1 in 100 chance of dying from COVID-19 and a 1 in 1,000,000 chance of getting a blood clot after the vaccine, it is far riskier to not be vaccinated and take my chances with COVID-19.
Thus far the mRNA vaccines by Pfizer and Moderna have been seen as the safest ones but there may soon be headlines across the UK saying “Pfizer jab linked with heart inflammation” or “Moderna jab causing heart problems in the young.”
With the UK now offering the Pfizer or Moderna vaccines to the under 40s, this is set to become a major cause of worry to that age group and could, yet again, set the vaccine programme back if people feel these vaccines are not safe.
(Click on the vaccine name to read dedicated pieces on each one.)
Pfizer/Moderna and Heart Problems: The Background
This latest concern is about a rare heart condition called myocarditis. Myocarditis is an inflammation (or swelling) of the heart muscle and can be caused by infections, especially viral infections. COVID-19 itself can cause myocarditis. Other causes include potent drugs such as cancer treatments and autoimmune diseases where the body attacks itself. It causes chest pain, a rapid heartbeat, shortness of breath and flu-like symptoms. (1)
Most "natural" cases of myocarditis are in young adults with males affected more often than females. The vast majority of cases resolve without complications but a minority lead to serious heart problems and can be fatal.
Over 3 million people worldwide will develop myocarditis each year. (2)
The Pfizer and Moderna vaccines are both mRNA vaccines. This is a new technology and different to that used in the AstraZeneca and other vaccines.
There have been reports of myocarditis in adolescents and young people following mRNA vaccination.
Males were more affected than females and cases were more common after the second dose, usually occurring within four days of receiving the second dose. Most of the cases were mild. (3)
What exactly has been found so far?
In late April Israel's Health Ministry reported it was looking into a small number of reported cases of myocarditis in people who had received the Pfizer vaccine. It had been found in 62 people, nearly all of whom were men under the age of 30, out of a total of 5 million people who had received the Pfizer vaccine. Two people died from myocarditis, a man aged 35 and a woman aged 22.
However, this rate of myocarditis in Israel was consistent with the normal background number of cases that occur leaving it unclear if the vaccine was a potential cause or the cases of myocarditis would have occurred anyway. If there is a link with the vaccine, the risk based on these Israeli figures would be 0.001%.
In the USA the CDC (Centers for Disease Control and Prevention) has noted that some teenagers and young adults, again nearly all men, have presented with myocarditis post vaccination with the Pfizer or Moderna vaccine. The CDC has recommended further investigation but, like Israel, has noted that the number of cases thus far identified is consistent with the normal background case rate. (4) (5)
Benjamin Haynes, a spokesman for the CDC told the Washington Post that: “Reported cases appear to be mild and often go away without requiring treatment,” and “the reports are rare given the number of vaccine doses administered.”
Regulators in Europe have noted that some cases of myocarditis have also been reported in Europe after receiving the Pfizer vaccine but they do not think the vaccine is the cause. (6)
In Conclusion
The number of cases of myocarditis presenting post vaccination is consistent with the normal background incidence. The fact that the majority of patients have been young males is also consistent with the normal presentation. It is vital to remember that COVID-19 itself poses a far greater threat to the heart even for younger, healthy people.
1.84 billion doses of all the different COVID-19 vaccines have been administered worldwide. The USA has administered nearly 300 million doses of the mRNA vaccines alone at the time of writing. With so many doses now given, a direct link to severe side effects becomes easier to identify, not harder. The fact that incidences of myocarditis thus far are no higher than the number expected at any given time suggests that the association with the vaccines is a coincidence and not a correlation.
Any forthcoming headlines claiming that the vaccine is causing heart problems in the young should be viewed with caution.
(6) WaPo 25 May CDC probes rare cases of heart inflammation in vaccinated teens, young adults May 25, 2021 at 12:18 a.m. GMT+1
