COVID-19 summer hospitalization increases in Korea in 2024 and 2025 coincided with shifts in dominant SARS-CoV-2 variants. We quantified variant-specific transmissibility and assessed how dominant variant transition could affect the 2026 summer epidemic.
Weekly hospitalization and viral sequence data from January 1, 2024 to January 19, 2026 were analyzed. Relative reproduction numbers were estimated from temporal changes in variant proportions using multinomial logistic regression and incorporated into an age-structured SEIHR-VD model for populations aged.