Risk of heart inflammation after mRNA Covid-19 vaccine very rare, DSRU study shows

The risk of heart inflammation after receiving an mRNA Covid-19 vaccine is very rare and mild in the vast majority of patients, according to the UK’s independent Drug Safety Research Unit (DSRU).

The DSRU reviewed data into the reported events of myocarditis and pericarditis following vaccinations with the mRNA Covid-19 vaccines from Pfizer/BioNTech and Moderna.

Myocarditis and pericarditis is an inflammation of the heart muscle and the protective sack that surrounds the organ. Symptoms after vaccination have included chest pain, shortness of breath and palpitations.

DSRU’s research found that events were very rare, and most cases were mild with those vaccinated making a full recovery.

In the UK, as of August 4, 2021, there were 165 reported myocarditis events and 140 pericarditis events after either the Pfizer or BioNTech Covid-19 vaccine. Two of these events were fatal.

This equates to approximately 7.93 cases of myocarditis and 6.73 cases of pericarditis per million vaccinees who had received at least one dose of the Pfizer/ BioNTech vaccine.

Among vaccinees who received the Moderna vaccine, there were 29 reports of myocarditis and 25 reports of pericarditis. None were fatal. This equates to 2.07 cases of myocarditis and 1.79 cases of pericarditis per million vaccinees.

Data from the US and Europe shows events were more common in men and people aged under 30. Events appear to occur within a few days of vaccination and are more common after a second mRNA vaccine dose.

The DSRU’s review echoes previous findings that men and people under 30 are more likely to experience myocarditis and pericarditis after an mRNA COVID-19 vaccine.

The DSRU is now calling for larger-scale research to better understand heart events, especially as more younger people are due to start receiving vaccines.

So far, only data from spontaneous reporting – whereby healthcare professionals and patients report side effects are available. This means that cases may have been missed and that it’s difficult to gauge incidence rates.

Only mRNA vaccines have been approved for use in children older than 12, so as vaccination programmes around the world progress into younger age groups, rates of myocarditis and pericarditis need to be monitored.

Professor Saad Shakir, who led the DSRU study, said: “Our review shows a similar picture across the UK, Europe and America and confirms these are very rare adverse events. But very, very occasionally they are serious.

“All we have is passive spontaneously reported information at the moment, which is very good for detecting signals but, like all pharmacovigilance methods, has limitations. With proactive research, we can understand who is at greater risk and why. And we can introduce measures to protect them.”

Listen to our interview with professor Saad Shakir from the DSRU using the link below: 

https://soundcloud.com/medtalkpodcast/understanding-covid-19