Study Suggests COVID Vaccines Reduce Risk of Heart Failure and Blood Clots After COVID Infection

A new study published in Heart suggests that COVID-19 vaccine reduce risk of heart failure and blood clots in veins or arteries for at least 6 months after COVID infection.

Investigators at the University of Oxford studied electronic health records of 10.2 million vaccinated and 10.4 million unvaccinated COVID-naïve people in the United Kingdom, Spain, and Estonia from January to July 2021. The Alpha and Delta variants were predominant during the study period, and participants “included adults of all ages and those at high risk for poor COVID-19 outcomes.”

The study looked at many different outcomes, including myocarditis/pericarditis, myocardial infarction, heart failure, and deep vein thrombosis. The authors noted “reports of unusual blood clots after receipt of adenovirus-based COVID-19 vaccines (AstraZeneca and J&J)…adding that a link was found between mRNA vaccines (Pfizer and Moderna) and a small risk of myocarditis.” However, they caution that “SARS-CoV-2 infection can trigger cardiac and thromboembolic complications,” with “risk for serious complications remain[ing] high for up to a year after infection.” The risk of clots and myocarditis is “much higher after COVID-19 infection than after vaccination.”

The study authors concluded that “COVID-19 vaccination reduced the risk of post-COVID-19 cardiac and thromboembolic outcomes.” They also wrote that “these effects were more pronounced for acute COVID-19 outcomes, consistent with known reductions in disease severity following breakthrough versus unvaccinated SARS-CoV-2 infection.”

CIDRAP’s website has the release.