Children faced a substantially higher risk of rare heart complications from being infected with COVID-19 during the pandemic than from being vaccinated against the disease, finds a new UCL-led study which compared the two scenarios for the first time.
The study, published in The Lancet Child and Adolescent Health, looked at the electronic health records of nearly 14 million children in England under the age of 18 between 1 January 2020 and 31 December 2022. Of those, 3.9 million were diagnosed with COVID-19 during that period and 3.4 million vaccinated against it.
The researchers from UCL, Cambridge and Edinburgh found that, in line with the existing body of research, there was a risk of complications like blood clots and heart inflammation associated with having the COVID-19 vaccine. But they also found that, for children, this risk was "substantially lower" than the same risk of developing those complications after being infected with the virus.
The study is the first large-scale study comparing that risk in the two scenarios.
While the researchers said the relevance of their findings to the present day was limited because of all the new COVID-19 variations since 2022, co-author Professor Angela Wood, from the University of Cambridge, said there was "no reason" why their findings relating to the risk of the rare complications from children being vaccinated would have changed. They are calling for more research so future public health policy can be best informed.
The study also found that the risks children faced of the rare complications from having the vaccine lasted only a few weeks, whereas the same risks from getting COVID-19 lasted around a year.
The UK government's policy on children getting vaccinated evolved as the pandemic progressed and by Spring 2022 the country's vaccination programme had been extended to include all children aged five to 11 years old.
Co-author Professor Pia Hardelid (UCL Great Ormond Street Institute of Child Health), said:
"Parents and carers have faced difficult choices throughout the pandemic. 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."
Professor Wood added: "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.
"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."
The study looked at children who had vaccinated with the COVID-19 BNT162b2 (Pfizer-BioNTech) vaccine, the main vaccine used in five to 18-year-olds during the study period.
The researchers analysed short- and long-term risks of rare complications including arterial and venous thrombosis (clots in blood vessels), thrombocytopenia (low levels of platelets in the blood), myocarditis or pericarditis (inflammation of the heart and its surrounding tissue respectively), and inflammatory conditions after COVID-19 diagnosis or vaccination.
After a first COVID-19 diagnosis, risks of the five 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.
In 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.
Previous research 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.
All personal information that could identify individuals was stripped away and approved researchers accessed this data entirely within the NHS England Secure Data Environment (SDE), a secure data and analysis platform.
The study was supported from the BHF Data Science Centre at Health Data Research UK.
