• Qiong Wu, Jiayi Tong, Bingyu Zhang, Dazheng Zhang, Jiajie Chen, Yuqing Lei, Yiwen Lu, Yudong Wang, Lu Li, Yishan Shen, Jie Xu, L Charles Bailey, Jiang Bian, Dimitri A Christakis, Megan L Fitzgerald, Kathryn Hirabayashi, Ravi Jhaveri, Alka Khaitan, Tianchen Lyu, Suchitra Rao, Hanieh Razzaghi, Hayden T Schwenk, Fei Wang, Margot I Gage Witvliet, Eric J Tchetgen Tchetgen, Jeffrey S Morris, Christopher B Forrest, and Yong Chen.
• The Center for Health Analytics and Synthesis of Evidence (CHASE), Department of Biostatistics, Epidemiology, and Informatics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania (Q.W., J.T., D.Z., J.C., Y.Lei, Y.W.).
• Ann. Intern. Med. 2024 Feb 1; 177 (2): 165176165-176.

BackgroundThe efficacy of the BNT162b2 vaccine in pediatrics was assessed by randomized trials before the Omicron variant's emergence. The long-term durability of vaccine protection in this population during the Omicron period remains limited.ObjectiveTo assess the effectiveness of BNT162b2 in preventing infection and severe diseases with various strains of the SARS-CoV-2 virus in previously uninfected children and adolescents.DesignComparative effectiveness research accounting for underreported vaccination in 3 study cohorts: adolescents (12 to 20 years) during the Delta phase and children (5 to 11 years) and adolescents (12 to 20 years) during the Omicron phase.SettingA national collaboration of pediatric health systems (PEDSnet).Participants77 392 adolescents (45 007 vaccinated) during the Delta phase and 111 539 children (50 398 vaccinated) and 56 080 adolescents (21 180 vaccinated) during the Omicron phase.InterventionFirst dose of the BNT162b2 vaccine versus no receipt of COVID-19 vaccine.MeasurementsOutcomes of interest include documented infection, COVID-19 illness severity, admission to an intensive care unit (ICU), and cardiac complications. The effectiveness was reported as (1-relative risk)*100, with confounders balanced via propensity score stratification.ResultsDuring the Delta period, the estimated effectiveness of the BNT162b2 vaccine was 98.4% (95% CI, 98.1% to 98.7%) against documented infection among adolescents, with no statistically significant waning after receipt of the first dose. An analysis of cardiac complications did not suggest a statistically significant difference between vaccinated and unvaccinated groups. During the Omicron period, the effectiveness against documented infection among children was estimated to be 74.3% (CI, 72.2% to 76.2%). Higher levels of effectiveness were seen against moderate or severe COVID-19 (75.5% [CI, 69.0% to 81.0%]) and ICU admission with COVID-19 (84.9% [CI, 64.8% to 93.5%]). Among adolescents, the effectiveness against documented Omicron infection was 85.5% (CI, 83.8% to 87.1%), with 84.8% (CI, 77.3% to 89.9%) against moderate or severe COVID-19, and 91.5% (CI, 69.5% to 97.6%) against ICU admission with COVID-19. The effectiveness of the BNT162b2 vaccine against the Omicron variant declined 4 months after the first dose and then stabilized. The analysis showed a lower risk for cardiac complications in the vaccinated group during the Omicron variant period.LimitationObservational study design and potentially undocumented infection.ConclusionThis study suggests that BNT162b2 was effective for various COVID-19-related outcomes in children and adolescents during the Delta and Omicron periods, and there is some evidence of waning effectiveness over time.Primary Funding SourceNational Institutes of Health.

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