Heart-related adverse effects of mRNA Covid-19 vaccines are rare and mild, latest research shows

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  • More than two million people were evaluated for the risk of heart inflammation after Covid-19 vaccination.
  • The participants received either the Pfizer or Moderna vaccines.
  • Their risk of developing heart problems after getting vaccinated was found to be low.

A new study has found that the incidence of people developing acute myocarditis was rare and mild after receiving Covid-19 mRNA vaccines.

The study published in JAMA Network assessed possible adverse effects involving the heart after receiving either the Pfizer or Moderna Covid-19 vaccines. The study focussed on acute myocarditis, the inflammation of the middle layer of the heart wall.

The researchers enrolled more than two million people over 18 years who had received at least one dose of either mRNA vaccine in the United States between 14 December 2020 and 20 July 2021.

The study experts identified potential cases of postvaccine myocarditis based on reports from clinicians and by identifying hospitalisation within ten days of vaccine administration with a discharge diagnosis of myocarditis. At least two cardiologists independently examined all cases.

A rare and mild occurrence 

The study findings show that the occurrence of myocarditis is rare and cases are mild. The findings show that only 5.8 persons per million got the disease after the second dose.

There were 15 cases of confirmed myocarditis in the study cohort, two after the first dose and 13 after the second. However, after treatment, symptoms had resolved, and no patients required intensive care unit admission or readmission after being discharged.

The study authors say that the risk of vaccination outweighs the side effects from Covid-19 infection.

“Overall, vaccination-related myocarditis was a rare and mostly mild adverse event. Data from the Vaccine Adverse Event Reporting System indicate that it is not unique to just the Covid-19 mRNA vaccine. Moreover, this risk is small when weighed with the morbidity and mortality of Covid-19 infection, in which up to 28% of hospitalised patients showed signs of myocardial injury,” the study authors wrote in a research letter.

*For more Covid-19 research, science and news, click here. You can also sign up for our Daily Dose newsletter here.

READ | At least one long-term symptom in 37% of Covid patients, Oxford researchers find

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