A lot has been written about heart conditions, including myocarditis and pericarditis, in children after receiving the COVID vaccine. However, a new study reveals a higher risk of these heart conditions from a COVID infection.

Many of us who write about the COVID vaccine have frequently claimed that the cardiovascular and other risks from a COVID infection were much greater than the small risks from the vaccine. This study adds to the evidence supporting those claims.

As I usually do, I’ll review the new study and provide the key results.

COVID vaccine and heart issues study

In a paper to be published in December 2025 in The Lancet Child & Adolescent Health, Alexia Sampri, PhD, University of Cambridge, England, and colleagues used data from the National Health Service England Secure Data Environment. The infection cohort included 13,896,125 individuals younger than 18 (48.8% female, 71.7% white), 28.1% of whom had a COVID diagnosis between January 2020 and March 2022. The vaccination cohort included 9,245,395 individuals aged 5 to 17 (48.8% female, 72.3% White), of whom 36.9% received a first dose of the Pfizer Comirnaty® mRNA vaccine between August 2021 and December 2022.

Here are the key results:

• The 6-month absolute excess risks for myocarditis or pericarditis were 2.24 per 100,000 individuals after diagnosis versus before diagnosis or no diagnosis, and 0.85 per 100,000 individuals after vaccination versus before vaccination or no vaccination.
• A COVID diagnosis was associated with a 39% higher risk of venous thromboembolism, blood clots that block the flow of blood through the veins, beyond 12 months, compared with no diagnosis.
• It was also associated with a 42% increased risk of thrombocytopenia, a condition characterized by an abnormally low number of platelets.
• Additionally, it was linked to a 42% increased risk of myocarditis or pericarditis.
• In the first week after diagnosis of COVID, the researchers observed a 1484% greater risk for systemic inflammatory conditions, 490% higher risk for venous thromboembolism, a 364% higher risk for thrombocytopenia, a 346% higher risk for myocarditis or pericarditis, and a 233% higher risk for arterial thromboembolism.
• However, the researchers found that after the first week post-vaccination, there was a 617% higher risk of myocarditis or pericarditis. There were no consistent trends in arterial thromboembolism, venous thromboembolism, and thrombocytopenia with vaccination.

The researchers concluded:

Children and young people have higher risks of rare vascular and inflammatory diseases up to 12 months after a first COVID-19 diagnosis and higher risk of rare myocarditis or pericarditis up to 4 weeks after a first BNT162b2 vaccine, although the risk following vaccination is substantially lower than the risk following infection.

Summary

This study shows that the risk of cardiovascular events, such as myocarditis, pericarditis, and thrombocytopenia, is much higher in individuals with COVID infection compared to individuals who receive the vaccine.

However, some may point to the results that, within a week after vaccination, there is a 6.17 times higher risk of myocarditis and pericarditis. Importantly, after six months, there was a 2.64 times higher risk of those conditions in the infected cohort compared to the vaccinated cohort.

Clearly, the benefits of the COVID vaccine far outweigh the risks of COVID itself with respect to cardiovascular conditions. COVID is dangerous, and the vaccine is not.

Citations

• Sampri A, Shi W, Bolton T, Ip S, Knight R, Walker V, Denholm R, Raffetti E, Keene S, Allara E, Jiang X, Kontopantelis E, Denaxas S, Khunti K, Conrad N, Pagel C, Hardelid P, Sterne JAC, Brown KL, Whiteley WN, Cezard G, Wood AM; CVD-COVID-UK/COVID-IMPACT Consortium and the Longitudinal Health Wellbeing COVID-19 National Core Study. Vascular and inflammatory diseases after COVID-19 infection and vaccination in children and young people in England: a retrospective, population-based cohort study using linked electronic health records. Lancet Child Adolesc Health. 2025 Dec;9(12):837-847. doi: 10.1016/S2352-4642(25)00247-0. PMID: 41198364.

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