XK and influenza: In this phase 1/2 clinical trial evaluating the safety, reactogenicity, and immunogenicity of two mRNA-based seasonal influenza vaccines (mRNA-1020 and mRNA-1030) targeting both HA and NA, we demonstrate the proof of concept that mRNA-1020 and mRNA-1030 elicit similar HA-specific immune responses to HA-only vaccines, while also inducing NA-specific immune responses with no additional reactogenicity beyond an mRNA-based, HA-only-containing vaccine.