Effectiveness of Pfizer vaccine considerably lower among kids against omicron variant of COVID-19: JAMA

The 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.

A study was conducted to evaluate the association of symptomatic infection with prior vaccination with BNT162b2 to estimate VE among children and adolescents during Omicron variant predominance.

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 the 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.

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). 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% and among adolescents, the OR was 0.40 (95% CI, 0.29-0.56; estimated VE, 59.5%
• During month 2 after dose 2, among children, the OR was 0.71 and among adolescents, the OR was 0.83 (95% CI, 0.76-0.92; estimated VE, 16.6%
• Among adolescents, the booster dose OR 2 to 6.5 weeks after the dose was 0.29

Thus, 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.

Reference:

Association of Prior BNT162b2 COVID-19 Vaccination With Symptomatic SARS-CoV-2 Infection in Children and Adolescents During Omicron Predominance by Katherine E. Fleming-Dutra, et al. published in the JAMA.

doi:10.1001/jama.2022.7493

Keywords:

JAMA, BNT162b2, Pfizer-BioNTech, vaccine, Katherine E. Fleming-Dutra, Amadea Britton, Nong Shang, Gordana Derado, Ruth Link-Gelles, Emma K. Accorsi, Zachary R. Smith, Joseph Miller, Jennifer R. Verani, Stephanie J. Schrag,