COVID vax linked to smaller risk of heart problems than infection

Receiving the Pfizer–BioNTech vaccine for COVID-19 is associated with half the risk of developing rare but serious heart inflammation within six months compared to the risk after being diagnosed with COVID-19, according to the largest study of its kind in children under 18 years old.

Children and young people often experience mild symptoms or are asymptomatic following COVID-19 infection; however, a small number can develop serious diseases, such as myocarditis or pericarditis (inflammation of the heart and its surrounding tissue respectively), blood vessels becoming blocked due to blood clots (venous thromboembolism) and low platelet count (thrombocytopenia). The Pfizer–BioNTech vaccine has also been linked to rare cases of myocarditis or pericarditis in young people, especially among boys and young men.

With this in mind, the new study used health records from between January 2020 and December 2022, covering 98% of England’s population under 18 years old, to assess the short- and long-term risks of health conditions associated with COVID-19 diagnosis and vaccination, including arterial and venous thrombosis, thrombocytopenia, myocarditis or pericarditis, and inflammatory conditions. The study was led by scientists at the University of Cambridge, the University of Edinburgh and University College London (UCL), with support from the British Heart Foundation Data Science Centre at Health Data Research UK. The results were published in The Lancet Child & Adolescent Health.

After a first COVID-19 diagnosis, risks of the conditions studied were highest in the first four weeks and, for several conditions, stayed higher for up to 12 months, compared to children and young people without or before a diagnosis. By contrast, after COVID-19 vaccination, the team only saw a short-term higher risk in myocarditis or pericarditis in the first four weeks, compared to children and young people without or before vaccination. After that, the risk returned to the same level as the start of the study period.

Over six months, the research team estimated that COVID-19 infection led to 2.24 extra cases of myocarditis or pericarditis per 100,000 children and young people who had COVID-19. In those who were vaccinated, there were only 0.85 extra cases per 100,000 children and young people.

The importance of the new research

Previous research has showed that children and young people diagnosed with COVID-19 are at a higher risk of developing conditions like myocarditis, pericarditis and thrombocytopenia, compared to their peers who hadn’t had a COVID-19 diagnosis. But while many studies show that COVID-19 vaccines can help children to avoid severe illness and hospitalisation, some also report rare cases of myocarditis in young people shortly after receiving a COVID-19 vaccine, particularly for mRNA-based vaccines. This is said to be the first study directly comparing the longer-term risks of both COVID-19 diagnosis and vaccinations in children and young people.

“Using electronic health records from all children and young people in England, we were able to study very rare but serious heart and clotting complications, and found higher and longer-lasting risks after COVID-19 infection than after vaccination,” said Cambridge co-author Professor Angela Wood, Associate Director at the BHF Data Science Centre.

“Whilst vaccine-related risks are likely to remain rare and short-lived, future risks following infection could change as new variants emerge and immunity shifts. That’s why whole-population health data monitoring remains essential to guide vaccine and other important public health decisions.”

With the risk of rare heart complications following COVID-19 vaccination found to be substantially lower than the risk following infection, the authors said their study provides important evidence to inform vaccination policies and support risk-benefit discussions with caregivers and healthcare professionals when considering COVID-19 vaccination in children and young people.

“Parents and carers have faced difficult choices throughout the pandemic,” noted study co-author Professor Pia Hardelid, from UCL and the NIHR Great Ormond Street Hospital Biomedical Research Centre. “By building a stronger evidence base on both infection and vaccination outcomes, we hope to support families and healthcare professionals to make decisions grounded in the best available data.”

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