COVID-19 Vaccine Effectiveness Among Adolescents

Area of Science:

• Vaccinology
• Infectious Disease Epidemiology
• Adolescent Health

Background:

• Limited data exist on the long-term effectiveness of BNT162b2 and mRNA-1273 vaccines against severe COVID-19 in adolescents.
• Few studies have evaluated the effectiveness of mRNA-1273 or heterologous mRNA vaccine schedules in this age group.

Purpose of the Study:

• To estimate the vaccine effectiveness (VE) of primary COVID-19 vaccine (2-dose) schedules in adolescents aged 12 to 17 years.
• To assess VE against COVID-19-related hospitalization and SARS-CoV-2 infection over a 6-month follow-up period.

Main Methods:

• Nationwide, 1-to-1 matched cohort analyses were conducted in Denmark, Finland, Norway, and Sweden from May 2021 to April 2023.
• Kaplan-Meier estimator was used to compare cumulative incidences of hospitalization and infection between vaccinated and unvaccinated adolescents.
• Random-effects meta-analyses combined country-specific VE and risk differences.

Main Results:

• BNT162b2 vaccination showed 72.6% VE against COVID-19 hospitalization (RD -2.8 per 10,000).
• mRNA-1273 vaccination demonstrated 86.0% VE (RD -2.1 per 10,000), and heterologous schedules showed 80.7% VE (RD -5.5 per 10,000).
• Effectiveness estimates remained comparable during Omicron predominance and up to 12 months of follow-up.

Conclusions:

• Severe COVID-19 is rare in adolescents in the Nordic countries.
• BNT162b2, mRNA-1273, and heterologous mRNA vaccination schedules provide substantial protection against COVID-19-related hospitalizations in adolescents.
• Protection was maintained even during the Omicron variant period.