Rates of long COVID significantly lower among children compared to adults: Canadian study

Kindergarten children line up before entering class at Portage Trail Community School which is part of the Toronto District School Board (TDSB), on Tuesday, September 15, 2020. THE CANADIAN PRESS/Nathan Denette

A new study led by Canadian researchers has found that the rates of long COVID among children are substantially lower compared to adults.

The study, titled "Post–COVID-19 condition in children 6 and 12 months after infection," was published in the peer-reviewed journal JAMA Network Open on Thursday and looked at what proportion of children had symptoms that met the definition of long COVID, also known as post-COVID condition. The researchers looked at a cohort of more than 5,000 Canadian children from pediatric emergency departments and followed up with the children after 90 days, six months and 12 months.

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The World Health Organization defines pediatric post-COVID condition as having symptoms that develop within three months of a COVID-19 infection, last for at least two months, and "limit everyday function and ascertainment of developmental milestones," the study says.

At the six-month follow-up, six of the 1,152 children with positive tests had symptoms that met the definition of long COVID, while four of the 3,995 children with negative tests met the definition. After 12 months, there were eight of 1,192 children with positive tests and seven of 4,371 children with negative tests who met the definition.

In addition, the researchers also measured any quality-of-life reductions in the children and found that overall quality of life among children who tested positive for COVID-19 didn't significantly differ from those who tested negative.

It's unclear how common long COVID is among adults who become infected with SARS-CoV-2, but according to the researchers, estimates made in various studies range between 7.5 per cent and 45 per cent.

Comparatively, the researchers noted that "very few infected children" develop post-COVID condition, as only 0.67 per cent of the children in the cohort who tested positive met the definition of long COVID.

This is in contrast to some of the previously published research, such as a 2022 study conducted in Germany, which found that the prevalence of "moderate or severe" post-COVID symptoms among adolescent girls was 32 per cent. However, the Canadian researchers note that their study is the first to use the WHO's consensus definition of pediatric post-COVID condition.

The researchers acknowledged a few limitations to their study. Most notably, they said they weren't able to follow up with 30 per cent of the eligible participants, and the children who did participate in the follow-ups were more likely to have been infected by the Omicron variant, which is " less strongly associated" with long COVID. Additionally, 80 per cent of the study participants were under the age of eight, which means the results may be "less generalizable to older children," the researchers wrote.