Study compares heart risks of COVID-19 infection and vaccination, and the results may surprise you

A health-care worker prepares a shot of the Pfizer COVID-19 vaccine in La Paz, Bolivia, Jan. 7, 2025. (AP Photo/Juan Karita)

The risk of children developing rare but serious heart complications is higher after a COVID-19 infection than after vaccination, according to a new study.

Described as the largest research effort of its kind, scientists analyzed electronic health records for nearly 14 million children across England ages 18 and younger, representing 98 per cent of this population. In the period from January 2020 to the end of December 2022, 3.9 million of these children were diagnosed with COVID-19 while 3.4 million received a shot of the Pfizer–BioNTech vaccine.

The study results “didn’t really surprise” Dr. Isaac Bogoch, an infectious disease specialist. He told CTV News Channel that the issue still needs more research.

The study focused on potential short- and long-term complications such as inflammatory conditions, blood vessel clots, low platelet levels and inflammation of the heart or its surrounding tissue, which is known as myocarditis and pericarditis.

After a COVID-19 diagnosis, researchers found that the risk of developing such complications was highest in the first four weeks and remained elevated for up to a year in some instances. Following COVID-19 vaccination, researchers only saw a heightened risk for myocarditis or pericarditis in the first four weeks before risk levels returned to normal.

Over a period of six months, researchers estimate that COVID-19 infections led to 2.24 extra cases of myocarditis or pericarditis per 100,000 children, while vaccinations led to 0.85 extra cases per 100,000.

“Helpful data. Does it completely address this question? Not entirely,” said Dr. Bogoch, who was not involved with the study. He advised Canadians to listen to the National Advisory Committee on Immunization.

“Canada has a fantastic independent body that reviews all the data for vaccinations, not just for flu and COVID but for vaccines, for everything, and they have excellent data driven recommendations,” he said.

The study was led by scientists from the Universities of Cambridge and Edinburgh and University College London, with support from the British Heart Foundation. Alexia Sampri from the University of Cambridge’s cardiovascular epidemiology unit was the principal author.

“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,” Sampri said in a news release.

While previous research shows that children experience an elevated risk of rare but serious complications after both COVID-19 infections and vaccinations, the study demonstrated how the risks are not the same.

“Parents, young people, and children need reliable information to make decisions about their health,” co-author and University of Edinburgh neurology and epidemiology professor William Whiteley said. “Here we have shown that during the pandemic, risks of myocarditis and inflammatory illnesses were low for children and young people, and that they were less after COVID-19 vaccination than after COVID-19 infection.”

The study was published Tuesday in The Lancet Child and Adolescent Health medical journal.

“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,” study co-author and University of Cambridge health data professor Angela Wood said. “That’s why whole-population health data monitoring remains essential to guide vaccine and other important public health decisions.”

There are “should-be” and “may-be” categories for vaccination, Dr. Bogoch said.

“People at risk for severe manifestations of the virus, over the age of 65, underlying health conditions that put them at greater risk, institutionalization in a nursing home for example, and everyone else is in the ‘may-be vaccinated,’” he suggested.

He said it’s “fantastic” if people in the “may-be” category want to be vaccinated but encouraged people who have more questions to talk to a health-care provider.

With files from CTV News Journalist Joe Van Wonderen