HealthDay News — For adolescents, vaccination provided protection against critical COVID-19 during omicron predominance, but provided lower protection against omicron-associated hospitalization, according to a study published online March 30 in the New England Journal of Medicine.

Ashley M. Price, M.P.H., from the COVID-19 Response Team at the U.S. Centers for Disease Control and Prevention in Atlanta, and colleagues used a case-control, test-negative design to examine vaccine effectiveness against COVID-19 among children and adolescents aged 5 to 18 years. The odds of antecedent full vaccination (two doses of BNT162b2 mRNA vaccine) at 14 days before illness were compared among case patients (1,185 patients) and controls (1,627 patients) during periods coinciding with delta variant predominance (July 1, 2021, to Dec. 18, 2021) and omicron variant predominance (Dec. 19, 2021, to Feb. 17, 2022).

Eighty-eight percent of the case patients were unvaccinated and 14 case patients died. The researchers found that vaccine effectiveness against hospitalization for COVID-19 was 93 percent at two to 22 weeks after vaccination and 92 percent at 23 to 44 weeks after vaccination among adolescents aged 12 to 18 years during the delta-predominant period. Vaccine effectiveness was 40 percent against hospitalization for COVID-19, 79 percent against critical COVID-19, and 20 percent against noncritical COVID-19 among adolescents during the omicron-predominant period. For children aged 5 to 11 years, vaccination effectiveness against hospitalization was 68 percent during the omicron-predominant period.

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“Continued monitoring of vaccine effectiveness against severe COVID-19 will be important to inform vaccination strategies as the time since vaccination increases or if new severe acute respiratory syndrome coronavirus 2 variants emerge,” the authors write.

Several authors disclosed financial ties to the biopharmaceutical industry.

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