Speaker
Description
COVID-19 epidemics have repeatedly coincided with shifts in dominant variants, and summer hospitalization increases were observed in South Korea in 2024 and 2025. This study aims to quantitatively evaluate and forecast the impact of dominant variant transition on the scale of the 2026 summer epidemic in South Korea.
Hospitalization surveillance and SARS-CoV-2 sequence data from January 1, 2024, to January 19, 2026, were analyzed. Variant-specific relative transmissibility was estimated from temporal changes in variant proportions using multinomial logistic regression \cite{Obermeyer2022} and incorporated into an age-structured SEIHR-VD model for individuals aged <65 and >=65 years. The transmission rate was decomposed into variant-associated transmissibility and background transmission. Scenario analyses varied the timing of dominance and transmissibility of a new variant.
KP.3 and NB.1.8.1 became dominant in August 2024 and May 2025, with relative reproduction numbers of 1.07 and 1.25, respectively. Despite the higher transmissibility of NB.1.8.1, the weekly hospitalization peak declined from 1,441 to 459. In the 2026 scenarios, transmissibility had a greater effect on epidemic size than the timing of dominance. The largest epidemic was forecast under May dominance with high transmissibility, with a peak of 993 weekly hospitalizations and 7,655 cumulative hospitalizations. Adults aged >=65 years accounted for a large share of hospitalizations in all scenarios.
Bibliography
@article{Obermeyer2022,
author = {Obermeyer, Fritz and Jankowiak, Martin and Barkas, Nikolaos and Schaffner, Stephen F. and Pyle, Jesse D. and Yurkovetskiy, Leonid and Bosso, Matteo and Park, Daniel J. and Babadi, Mehrtash and MacInnis, Bronwyn L. and Luban, Jeremy and Sabeti, Pardis C. and Lemieux, Jacob E.},
title = {Analysis of 6.4 million {SARS-CoV-2} genomes identifies mutations associated with fitness},
journal = {Science},
year = {2022},
volume = {376},
number = {6599},
pages = {1327--1332},
doi = {10.1126/science.abm1208}
}
