New study: COVID-19 vaccine is safe for younger children, no link to side effects found

The analysis involved 135,000 doses of Pfizer-BioNTech's messenger RNA vaccine and 112,000 doses of Moderna's vaccine. The researchers found no association, within 21 days of vaccination, between the vaccine and 23 side effects. (Pfizer via AP)

A large-scale American study has found no association between vaccination against COVID-19 and some 20 side effects, some of them potentially serious, in toddlers aged between six months and five years.

The analysis, carried out by health organization Kaiser Permanente in collaboration with the U.S. Centers for Disease Control and Prevention, involved 135,000 doses of Pfizer-BioNTech messenger RNA vaccine and 112,000 doses of Moderna vaccine. These doses were administered between June 2022 and March 2023.

The researchers detected no association, within 21 days of vaccination, between the vaccine and 23 side effects ranging from appendicitis to Kawasaki syndrome.

"The conclusion is that this vaccine is safe for children under 12 years of age," summarized Dr. Caroline Quach-Thanh, from CHU Sainte-Justine.

"Crucially," write the authors of the study, "no association was found between vaccination and myocarditis or pericarditis, which is consistent with data from Phase 3 clinical studies or the findings of other vaccine monitoring systems."

The risk of myocarditis associated with COVID-19 vaccination had been seen primarily in boys and men aged 12 to 29, Quach-Thanh recalled.

"It's really in that age group where it was," she said. "But in younger children, it's not the same dose of vaccine –remember, there's a lower dose of messenger RNA in pediatric vaccines. The risk really seems to increase with adolescence. Is the immune response different? We don't really know."

The study shows that the COVID-19 messenger RNA vaccine is safe for children aged 12 and under, "period," reiterated Quach-Thanh.

Now, whether or not it should be given to children in whom vaccine efficacy will be very limited is a whole other debate that "has nothing to do with safety," she said.

"It's always good to prevent complications and hospitalizations, but there are virtually none in a healthy child," she said. "The reason why in Quebec vaccination of children for COVID has never been a strong recommendation, unless the child has an underlying medical condition, is that the benefit isn't that great."

There was a frenzy (media and otherwise) surrounding certain side effects that were associated, rightly or wrongly, with COVID-19 vaccination at the height of the pandemic.

Despite that, in the end, concludes Quach, this new study shows that vaccine side-effect monitoring systems are working, and said that's the most important and reassuring thing of all.

"If we want the public to continue to trust us when we say, look, the vaccine is safe, we have to be able to demonstrate that it's safe," she said. "We have to be able to detect small signals, even when it doesn't make sense. That's how science advances, and that's how we maintain a safe vaccination system."

The findings of this study were published in the renowned medical journal Pediatrics.

This report was first published in French by The Canadian Press on June 19, 2023.