Effectiveness of NVX-CoV2373 and BNT162b2 COVID-19 Vaccination in South Korean Adolescents.

Background and aims: Adolescents can have severe/chronic outcomes from COVID-19. Real-world data on relative vaccine effectiveness between mRNA- and protein-based vaccines are limited, and more data are needed on disease outcomes in this age group.

Methods: The K-COV-N database, COVID-19 vaccine registry and health insurance claims were retrospectively reviewed to identify adolescents (12- to 18-year-olds) in South Korea who received a homologous primary series of NVX-CoV2373 or BNT162b2 and a heterologous or homologous third vaccine dose. Vaccine recipients were propensity score matched to reduce confounding baseline factors. Adjusted hazard ratios (aHRs) for any medically attended COVID-19 postvaccination (starting 14 days after primary series and 7 days after a third dose) were calculated to assess relative vaccine effectiveness every 30 days through a 180-day risk window.

Results: From February to December 2022, 3174 and 6253 doses of NVX-CoV2373 and BNT162b2, respectively, were administered to South Korean adolescents. Individuals who received NVX-CoV2373 tended to be older, have a disability, and/or have a prior SARS-CoV-2 infection. Propensity score matching resulted in 107 individuals in each primary series group and 701 and 1417 individuals in the NVX-CoV2373 and BNT162b2 third-dose groups, respectively. The aHR (95% CI) for NVX-CoV2373 compared with BNT162b2 for medically attended COVID-19 in the 180-day risk window was 0.57 (0.31-1.05) for the primary series and 0.68 (0.54-0.84) for the third dose.

Conclusions: These results suggest that NVX-CoV2373 may provide more robust protection against medically attended COVID-19 as a third dose, compared with BNT162b2. While the aHR for the primary series also indicated lower risk with NVX-CoV2373, this difference was not statistically significant.