Heart complications risk in children ‘greater after Covid infection than vaccination’

The risk of rare cardiovascular complications in children is substantially greater after Covid-19 infection than following vaccination against the disease, a new study has shown.

Researchers found that children and young people had a long-lasting increased risk of heart complications following a Covid-19 infection.

While an increase in myocarditis and pericarditis was observed after both infection and vaccination, the risk linked to Covid-19 vaccination was short-term, lasting only for a few weeks, and much smaller than that linked to Covid-19 infection.

Led by researchers from the University of Cambridge, University of Edinburgh and University College London (UCL), and supported by the British Heart Foundation (BHF), the findings are published in The Lancet Child & Adolescent Health, highlighting the importance of monitoring long-term health conditions following Covid-19 infection.

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Previous studies have shown that children diagnosed with Covid-19 infection are at an increased risk risk of developing heart complications, and some studies have shown rare cases of myocarditis in young people shortly after receiving a Covid-19 vaccine, particularly for mRNA-based vaccines.

This is the first study to examine the long-term risks to children of heart and inflammatory conditions for both Covid infection and vaccination.

The researchers analysed the electronic health records of nearly 14 million children in England registered at a GP surgery.

All children were under the age of 18 between 1 January 2020 and 31 December 2022, with the cohort representing 98 per cent of the population in this age group. From this data set, 3.9 million children were diagnosed with a first Covid-19 infection during that period, and 3.4 million received a first dose of the Pfizer–BioNTech (BNT162b2) vaccine, which was the most frequently used vaccine for children between the ages of five and 18.

The records were analysed for the short- and long-term risks of arterial thrombotic events, venous thrombotic events, thrombocytopenia, myocarditis, pericarditis and inflammatory conditions, examining the risks in the four weeks after infection or vaccination.

The absolute risk of heart and inflammatory conditions remained very low in both cases, but was more significant in children who had been infected with the Covid-19 virus than those who received the vaccine.

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There were 2.24 extra cases of myocarditis or pericarditis per 100,000 children in children infected by the Covid-19 virus. In children who received the Covid-19 vaccine, the researchers reported an additional 0.85 cases per 100,000 children.

After a first Covid-19 diagnosis, the risks of each condition were increased, particularly in the first month after diagnosis, with some risks remaining elevated up to 12 months after diagnosis, compared to children and young people without or before a diagnosis.

Principal author Dr Alexia Sampri, from the Cardiovascular Epidemiology Unit at the University of Cambridge, said: ‘Our whole-population study during the pandemic showed that although these conditions were rare, children and young people were more likely to experience heart, vascular or inflammatory problems after a Covid-19 infection than after having the vaccine and the risks after infection lasted much longer.’

In contrast, the researchers reported only a short-term increased risk of myocarditis or pericarditis, primarily within the first four weeks after the Covid-19 vaccination. Beyond this period, there was no observable increased risk.

Co-author Professor Angela Wood, University of Cambridge and associate director at the BHF Data Science Centre, added: ‘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.’

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The researchers say their findings help build a stronger evidence base, enabling families and healthcare professionals to make informed decisions about Covid-19 vaccination and the risks of infection.