Study Design and Participants
This was a phase 3, randomized, open-label, multicenter clinical trial conducted in the US. Eligible adults were randomly assigned (1:1) to receive coadministration of a booster dose (50 µg) of mRNA-1273 and the first dose of RZV (RZV1) (Coad group), or the mRNA-1273 booster followed 2 weeks later by RZV1 (Sequential [Seq] group). All study participants received the second dose of RZV (RZV2) 2 months post-RZV1 and were followed for safety endpoints until 6 months post-RZV2 (ClinicalTrials.gov identifier NCT05047770).Eligible adults aged ≥50 years were healthy or medically stable who had completed a 2-dose mRNA-1273 primary vaccination series at least 6 months prior to study vaccination. A full list of eligibility criteria is provided in the The study was conducted according to the Good Clinical Practice guidelines of the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use and ethical principles derived from the Declaration of Helsinki. The protocol was approved by all applicable institutional review boards (Advarra Institutional Review Board, Western Copernicus Group Institutional Review Board). Written informed consent was obtained from each participant prior to enrollment.