Real-world study of Pfizer vaccine in children finds moderate Omicron protection

A field study in Israeli children ages 5 to 11 found that the Pfizer-BioNTech vaccine provided moderate protection against infection and symptomatic disease, similar to the pattern seen in adults.

Researchers began measuring the vaccine’s impact last November, just as the increase in the Omicron variant spread worldwide. They published their findings yesterday in the New England Journal of Medicine (NEJM).

Similar protection against infection and symptoms

Using data from the nation’s largest healthcare organization, they included 94,728 vaccinated children compared to unvaccinated controls. To assess the effectiveness of the vaccine, they examined the documented infection 14 to 27 days after the first dose and 7 to 21 days after the second dose.

During the study period, children were tested after coming into contact with an infected person or applying for a “green pass”, a certificate that allowed vaccinated or recovered people to participate in cultural activities or travel abroad.

The study period ended on January 7 this year, when Israel implemented a new testing policy that allowed vaccinated people to use rapid tests at home.

After one dose, researchers estimated vaccine effectiveness at 17% (95% confidence interval [CI], 7 to 25), and after two doses, vaccine efficacy was 51% (95% CI, 39 to 61). They also estimated that the vaccine was 48% effective against symptomatic disease 1 to 3 weeks after the second dose, which they say is lower than the estimated 90.7% efficacy when the Delta variant was dominant.

They noted that the effectiveness may be greater in younger children, ages 5 and 6, compared to older children. The estimate was 68% (95% CI, 43 to 84) effective after the second dose.

Given the limitation of the short follow-up period due to the change in testing policy, the authors said follow-up to assess impact on serious outcomes such as hospitalization was not possible. They wrote that more studies are needed to look at longer-term effectiveness and to examine dose effects in different age groups.

Practical data useful for policy management, but questions remain

In a NEJM In an audio interview about the study, Lindsey Baden, MD, deputy editor-in-chief, said the work highlights the speed needed to understand COVID to make more informed clinical and public health decisions.

However, Eric Rubin, MD, said policy changes, for example, could add challenges to collecting real-world tests over a significant period of time. He said some of the key findings are that one dose didn’t provide much protection and the second dose provided only moderate protection, which wasn’t surprising given Omicron was dominant.

“Overall, I think these data suggest that the benefits of vaccination are probably the same in children as they are in adults, but we are missing important data,” Rubin said.

Leave a Comment