‘Moderate’ Vax Protection Against Omicron for Young Kids

Protection against Omicron in children ages 5-11 years was minimal following a single dose of Pfizer/BioNTech’s COVID-19 vaccine, but hovered around 50% following the second dose, a large observational study from Israel found.

In the 14 to 27 days after the first dose of BNT162b2, vaccine effectiveness (VE) against Omicron was 17% for a documented infection (95% CI 7-25) and 18% for a symptomatic case (95% CI -2 to 34), reported Noa Dagan, MD, PhD, of the Clalit Research Institute in Tel Aviv, and colleagues.

But VE grew to 51% (95% CI 39-61) and 48% (95% CI 29-63), respectively, in the 14 to 27 days following the second dose, according to the findings.

“Vaccination with BNT162b2 showed moderate protection against documented SARS-CoV-2 infection and symptomatic COVID-19 among children 5 to 11 years of age,” Dagan’s group wrote in the New England Journal of Medicine. “However, protection was not uniform across all ages.”

Trends toward higher VE for both infection and symptomatic cases, respectively, were observed in younger versus older children:

  • 5-6 years: 68% and 69%
  • 7-9 years: 56% and 49%
  • 10-11 years: 38% and 36%

This “is consistent with recent findings showing that the protection provided by the pediatric formulation may be lower in the older children (within the range of 5 to 11 years of age) than in the adolescents who received a higher dosage,” the group noted.

In the current study, analyses for severe outcomes were not possible, the researchers noted, as hospitalizations were exceedingly uncommon: one among the vaccinated kids and two among the unvaccinated. Of note, few children had CDC risk factors for severe COVID-19, with asthma (3.7%) and chronic kidney disease (1.8%) being the most common.

But past data have demonstrated protection against severe outcomes from the highly contagious Omicron variant, with vaccinated U.S. kids ages 5-11 having twice the protection against COVID-related hospitalization compared with unvaccinated children.

For their study, Dagan and colleagues looked at 94,728 kids ages 5-11 years in Israel who were vaccinated with Pfizer’s COVID-19 vaccine during the study period (Nov. 23, 2021 to Jan. 7, 2022). They were matched to an equal number of unvaccinated controls. The population came from the nation’s largest healthcare provider, Clalit Health Services.

Median patient age was 8 years, and 17% were overweight or with obesity. Two-thirds had no chronic conditions, based on diagnostic codes, while 19% had one, and 14% had two or more conditions.

Dagan’s group noted “minimal differences in risk” between groups in the time after the first dose. The earliest possible event (infection or a symptomatic case) following the second dose was Dec. 21, 2021, when Omicron was responsible for two-thirds of cases and quickly becoming even more dominant in Israel.

Among the 22,109 children in each group with sufficient follow-up after the second dose, 201 infections and 68 symptomatic cases were recorded in the fully vaccinated group versus 423 infections and 133 symptomatic cases in the unvaccinated group.

Following the second dose, the researchers estimated 1,905 more documented infections per 100,000 for unvaccinated individuals and 1,599 more cases of symptomatic COVID-19 per 100,000 during follow-up.

As in all observational studies, the possibility for residual confounding was possible, the study authors noted. For example, no information on mask-wearing habits was available. But cases between groups were very similar at the start of follow-up, suggesting that confounding was likely minimal.

Short follow-up due to testing changes in Israel represented another important limitation; “therefore, this study addresses only the question of short-term effectiveness soon after vaccination,” Dagan and co-authors acknowledged.

  • Ian Ingram is Managing Editor at MedPage Today and helps cover oncology for the site.


The study was funded by the European Union.

Dagan and some co-authors reported institutional grants to the Clalit Research Institute from Pfizer unrelated to the current study. Other co-authors disclosed relationships with Cytel, Bristol Myers Squibb, the CDC, Janssen, Merck, the NIH, Pfizer, Sanofi, and United Biomedical.

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