COVID-19 infections are more likely to trigger rare cardiovascular complications such as heart inflammation and irregular heartbeat than vaccines, a British study showed on Tuesday, after scientists parsed data of about 38 million vaccinated people.
The study, published in the Nature Medicine journal, compared the risks of myocarditis, pericarditis and cardiac arrhythmia following a first and second dose of COVID-19 vaccines – from AstraZeneca-Oxford, Pfizer-BioNTech and Moderna - with coronavirus infections.
The study, led by Oxford University researchers, found an increased risk of myocarditis with first doses of AstraZeneca-Oxford and Pfizer-BioNTech vaccines and both doses of Moderna's shot, but the risk was much higher after a COVID-19 infection.
Conclusions were arrived at by assessing rates of hospitalizations or death from the conditions within 28 days of vaccination or a positive PCR test for individuals 16 years and older and vaccinated between Dec. 1, 2020 and Aug. 24, 2021.
"We estimated between 1 and 10 extra events of myocarditis in 1 million people vaccinated with a first or second dose, but 40 extra cases in 1 million people infected with COVID-19," Oxford professor and study lead Julia Hippisley-Cox said.
An analysis by age also showed that higher risk of myocarditis associated with mRNA vaccines from Pfizer-BioNTech and Moderna was present only in those younger than 40 years of age, researchers said.
"The observation (on heart conditions) ... is not new information. We already know this. But this solid, scientifically robust paper supports and confirms this," said Dr. Peter English, a retired consultant in communicable disease control.