Immunogenicity of JN.1- and KP.2-Encoding mRNA COVID-19 Vaccines Against 1 JN.1 Subvariants in Adult Participants

COVID-19 vaccines encoding JN.1 (mRNA-1273.167) and KP.2 (mRNA-1273.712) were approved for the immunization programs for the 2024-2025 season. This ongoing, open-label, phase 3b/4 study evaluated the safety and immunogenicity of mRNA-1273.167 and mRNA-1273.712 against vaccine-matched variants and JN.1-lineage subvariants (KP.3.1.1, XEC, LP.8.1) in adults with previous COVID-19 mRNA vaccination. Each of the two groups independently enrolled 50 participants. Both JN.1 and KP.2 vaccines increased neutralizing antibody responses at Day 29 against vaccine-matched variants, as well as against KP.3.1.1, XEC, and LP.8.1. Reduction in cross-neutralization was observed across all tested subvariants compared with the reference variant JN.1. No safety concerns were identified.