Virological characteristics of the SARS-CoV-2 XEC variant

The SARS-CoV-2 JN.1 (BA.2.86.1.1) variant, arising from BA.2.86.1 with spike protein (S) substitution S:L455S, outcompeted the previously predominant XBB lineages by the beginning of 2024.1 Subsequently, JN.1 subvariants including KP.2 (JN.1.11.1.2) and KP.3 (JN.1.11.1.3), which acquired additional S substitutions (eg, S:R346T, S:F456L, and S:Q493E), have emerged concurrently (appendix pp 19–20).2,3 As of October 2024, KP.3.1.1 (JN.1.11.1.3.1.1), which acquired S:31del, outcompeted other JN.1 subvariants including KP.2 and KP.3, and is the most predominant SARS-CoV-2 variant in the world.