Mellis et al. show that the SARS-CoV-2 JN.1 sublineage has different virological features associated with its recently dominant subvariants. LP.8.1 has greater receptor-binding affinity than earlier strains but not increased antibody evasion, while the more recently dominant XFG and NB.1.8.1 have greater antibody evasion than LP.8.1.1.