Association of Prior BNT162b2 COVID-19 Vaccination With Symptomatic SARS-CoV-2 Infection in Children and Adolescents During Omicron Predominance.

Importance: Efficacy of 2 doses of the BNT162b2 COVID-19 vaccine (Pfizer-BioNTech) against COVID-19 was high in pediatric trials conducted before the SARS-CoV-2 Omicron variant emerged. Among adults, estimated vaccine effectiveness (VE) of 2 BNT162b2 doses against symptomatic Omicron infection was reduced compared with prior variants, waned rapidly, and increased with a booster.

Objective: To evaluate the association of symptomatic infection with prior vaccination with BNT162b2 to estimate VE among children and adolescents during Omicron variant predominance.

Design, Setting, and Participants: A test-negative, case-control analysis was conducted using data from 6897 pharmacy-based, drive-through SARS-CoV-2 testing sites across the US from a single pharmacy chain in the Increasing Community Access to Testing platform. This analysis included 74 208 tests from children 5 to 11 years of age and 47 744 tests from adolescents 12 to 15 years of age with COVID-19-like illness who underwent SARS-CoV-2 nucleic acid amplification testing from December 26, 2021, to February 21, 2022.

Exposures: Two BNT162b2 doses 2 weeks or more before SARS-CoV-2 testing vs no vaccination for children; 2 or 3 doses 2 weeks or more before testing vs no vaccination for adolescents (who are recommended to receive a booster dose).

Main Outcomes and Measures: Symptomatic infection. The adjusted odds ratio (OR) for the association of prior vaccination and symptomatic SARS-CoV-2 infection was used to estimate VE: VE = (1 - OR) × 100%.

Results: A total of 30 999 test-positive cases and 43 209 test-negative controls were included from children 5 to 11 years of age, as well as 22 273 test-positive cases and 25 471 test-negative controls from adolescents 12 to 15 years of age. The median age among those with included tests was 10 years (IQR, 7-13); 61 189 (50.2%) were female, 75 758 (70.1%) were White, and 29 034 (25.7%) were Hispanic/Latino. At 2 to 4 weeks after dose 2, among children, the adjusted OR was 0.40 (95% CI, 0.35-0.45; estimated VE, 60.1% [95% CI, 54.7%-64.8%]) and among adolescents, the OR was 0.40 (95% CI, 0.29-0.56; estimated VE, 59.5% [95% CI, 44.3%-70.6%]). During month 2 after dose 2, among children, the OR was 0.71 (95% CI, 0.67-0.76; estimated VE, 28.9% [95% CI, 24.5%-33.1%]) and among adolescents, the OR was 0.83 (95% CI, 0.76-0.92; estimated VE, 16.6% [95% CI, 8.1%-24.3%]). Among adolescents, the booster dose OR 2 to 6.5 weeks after the dose was 0.29 (95% CI, 0.24-0.35; estimated VE, 71.1% [95% CI, 65.5%-75.7%]).

Conclusions and Relevance: Among children and adolescents, estimated VE for 2 doses of BNT162b2 against symptomatic infection was modest and decreased rapidly. Among adolescents, the estimated effectiveness increased after a booster dose.