[Prevalence of Recent COVID-19 Variants and Cell-based Omicron KP.3 Infectivity Analysis]

Since the outbreak of the coronavirus disease (COVID-19) pandemic in 2019, the Korea Disease Control and Prevention Agency (KDCA) has been conducting genomic surveillance using whole-genome sequencing to monitor SARS-CoV-2 variants in the Republic of Korea (ROK). Since the JN.1 lineage, derived from BA.2.86, was first detected in ROK in November 2023, the proportion of various JN.1 sub-lineages has continued to increase, with KP.3 accounting for 60.9% as of August 2024. In particular, the KP.3 sub-lineages with the highest shares were identified as KP.3.3.1 (22.3%), KP.3.3 (14.0%), and KP.3.1.1 (11.1%). We compared cell-based infectivity and viral replication among recently circulating JN.1, KP.2, and KP.3. KP.3 showed the highest viral shedding rate up to 48 hours, especially at 24 hours, when it was approximately 67 times higher than that of JN.1 and 23 times higher than that of KP.2. Although there was little difference in peak viral replication among JN.1, KP.2, and KP.3, that of KP.3 was approximately 66 and 16 times higher than that of JN.1 and KP.2, respectively, at 24 hours. We hypothesize that the higher initial infectious virus shedding and viral replication of KP.3 compared to those of JN.1 and KP.2 may have contributed to the increase in transmission and cases. The KDCA will continue close monitoring based on whole-genome sequencing to identify the prevalence of variants in ROK, characterize new variants, and provide scientific evidence to guide the COVID-19 response in the country.