Pfizer COVID-19 vaccine protects kids against infection, is less effective against omicron
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The Pfizer-BioNTech COVID-19 vaccine reduced the risk for infection with the omicron variant of SARS-CoV-2 by 31% among children aged 5 to 11 years and 59% among adolescents aged 12 to 15 years, according to data published Friday in MMWR.
The real-world study also found that the vaccine was 87% effective against infection with the delta variant among adolescents. The variant surged before younger children had access to the vaccine.
“Real-world data on vaccine effectiveness (VE) in these age groups are needed, especially because when the omicron variant became predominant in the United States in December 2021, early investigations of VE demonstrated a decline in protection against symptomatic infection for adolescents aged 12-15 years and adults,” CDC COVID-19 Emergency Response Team member Ashley L. Fowlkes, ScD, and colleagues wrote.
In a statement, the CDC noted that data published last week showed that the vaccine’s effectiveness against COVID-19-associated hospitalization ranged from 92% to 94% among adolescents aged 12 through 17 years during the delta surge to 74% in children aged 5 to 11 years during the omicron surge.
The new study “reinforces the importance of vaccination to keep children and teens protected from severe disease and out of the hospital.”
“COVID-19 vaccination remains a safe and critical tool to protect children and teens regardless of their health status,” the CDC said.
Fowlkes and colleagues analyzed data from PROTECT, a prospective cohort study monitoring SARS-CoV-2 infections among participants aged 6 months to 17 years in four states Arizona, Florida, Texas and Utah.
The study enrolled of 1,364 participants — 1,052 children aged 5 to 11 years and 312 adolescents aged 12 to 15 years — who were tested at least weekly between July 25, 2021, and Feb. 12, 2022. Most of the participants lived in Arizona.
Among the younger age group, the effectiveness of two doses of the vaccine was 31% (95% CI, 9%-48%) when adjusted for sociodemographic characteristics, health information, frequency of social contact, mask use, location and local virus circulation, Fowlkes and colleagues reported. Among adolescents aged 12 to 15 years, it was 87% (95% CI, 49%-97%) against symptomatic and asymptomatic delta infection and 59% (95% CI, 22%-79%) against omicron infection.
The researchers also reported that, among unvaccinated participants with SARS-CoV-2 infection, those infected with the delta variant were more likely to report COVID-19 symptoms (66%) than were those with omicron infections (49%).
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