COVID vaccines halved infection in kids during winter, Israeli study finds

Biggest study of its kind checked medical records of almost 100k children at height of winter wave; found 51% effectiveness against infection and 48% against symptomatic infection

Nathan Jeffay is The Times of Israel's health and science correspondent

A child receives a COVID vaccine in Jerusalem on December 30, 2021. (Olivier Fitoussi/Flash90)
A child receives a COVID vaccine in Jerusalem on December 30, 2021. (Olivier Fitoussi/Flash90)

The world’s largest study on COVID vaccines and kids has found that they halved the risk of COVID infection during Israel’s winter wave.

The authors characterized this result as “moderate” protection — a far cry from the very high level of protection vaccines initially provided, but much better that some earlier estimations that suggested that vaccines were giving children just 12% protection against infection with newer strains.

The newly peer-reviewed study, led by Clalit Healthcare Services, one of Israel’s four healthcare providers, compared COVID records of 94,728 Pfizer-vaccinated children and the same number of unvaccinated children with similar age and health profiles. All children in the study, conducted at the height of Israel’s winter wave, were aged 5 to 11.

Researchers found that during the two weeks after children’s second dose kicked in, they had 51% protection against becoming infected. Protection against infection with symptoms was 48%.

“I think 48% to 51% is still pretty high,” Prof. Ben Reis, one of the study’s authors, told The Times of Israel. “It’s true that we got used to seeing percentages in the 90s for protection level [when vaccines initially came out], but protecting against half of infections and illnesses is still a real advantage.”

Reis, a senior researcher with the Clalit Research Institute and Harvard Medical School, said that the study, just published in the New England Journal of Medicine, will have international resonance. “As a very large controlled study on the real world effectiveness of pediatric Pfizer vaccines, this adds to the evidence base for parents to enable them to make informed decisions about vaccinating their children,” he noted.

An Israeli child takes a coronavirus test (Michael Giladi/Flash90)

He stressed that at the time of the research, vaccine effectiveness against infection for adults had already dipped from well over 90% early in the pandemic to 65.5% when faced with the immunity-defying Omicron variant.

Reis said that the emerging picture is that children seem to be somewhat less protected by vaccines than adults, for reasons that aren’t yet clear — but not dramatically so. Pfizer is expected to soon release vaccines that are more effective against variants, and Reis expects effectiveness will rise for both adults and children. He commented: “The main issue here appears not to be an issue with vaccines and children, but that ever-evolving variants are an issue for kids and adults alike.”

Reis added: “We’ve been ‘spoilt’ with the very high vaccine effectiveness levels earlier in the pandemic — numbers of 90-plus percent. We’ve been using the same vaccine all long and now we’re a few variants along but the vaccine is the same. So while these figures sound low, taken in context, this isn’t necessarily the case.”

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