Effectiveness of BNT162b2 vaccine against SARS-CoV-2 Delta and Omicron infection in adolescents, Norway, August 2021 to January 2022. (May 2023)

• Record Type: Journal Article
• Authors: Veneti, Lamprini; Berild, Jacob Dag; Watle, Sara Viksmoen; Starrfelt, Jostein; Greve-Isdahl, Margrethe; Langlete, Petter; Bøås, Håkon; Bragstad, Karoline; Hungnes, Olav; Meijerink, Hinta
• Is Part Of: International journal of infectious diseases. Volume 130(2023)
• Page Start: 182
• Page End: 188
• Publication Date: 2023-05
• Subjects: Vaccine effectiveness -- BNT162b2 -- Delta -- Omicron -- Adolescents -- SARS-CoV-2; Communicable diseases -- Periodicals; Communicable Diseases -- Periodicals; Communicable diseases; Periodicals; Electronic journals; 616.9
• DOI: 10.1016/j.ijid.2023.03.004
• Languages: English
• ISSNs: 1201-9712

Abstract

Highlights: The BNT162b2 vaccine was less effective against any Omicron infection than Delta. The effectiveness decreased with time since vaccination for both Delta and Omicron. We did not observe a protective effect against Omicron infection after one dose. The vaccine effectiveness against Delta peaked at 93% in 35-62 days after the second dose. The vaccine effectiveness against Omicron peaked at 53% in 7-34 days after the second dose. Abstract: Objectives: We estimated the BNT162b2 vaccine effectiveness (VE) against any (symptomatic or not) SARS-CoV-2 Delta and Omicron infection among adolescents (aged 12-17 years) in Norway from August 2021 to January 2022. Methods: We used Cox proportional hazard models, where vaccine status was included as a time-varying covariate and models were adjusted for age, sex, comorbidities, residence county, birth country, and living conditions. Results: The VE against Delta infection peaked at 68% (95% confidence interval [CI]: 64-71%) and 62% (95% CI: 57-66%) in days 21-48 after the first dose among those aged 12-15 years and 16-17 years, respectively. Among those aged 16-17 years who received two doses, the VE against Delta infection peaked at 93% (95% CI: 90-95%) in days 35-62 and decreased to 84% (95% CI: 76-89%) in ≥63 days after vaccination. We did not observe a protective effect against Omicron infection after receiving one dose. Among those aged 16-17 years, the VE against Omicron infection peaked at 53% (95% CI: 43-62%) in 7-34 days after the second dose and decreased to 23% (95% CI: 3-40%) in ≥63 days after vaccination. Conclusion: We found a reduced protection after two BNT162b2 vaccine doses against any Omicron infection compared to Delta. Effectiveness decreased with time from vaccination for both variants. The impact of vaccination among adolescents on reducing infection and thus transmission is limited during the Omicron dominance.