A Study to Evaluate the Safety and Immune Response of mRNA-1345, a Vaccine Targeting Respiratory Syncytial Virus (RSV), When Co-administered With a Fluzone HD, in Adults ≥65 Years of Age

Summary

The main purpose of this study is to evaluate the safety and immunogenicity of mRNA-1345 RSV vaccine when coadministered with a high dose (HD) quadrivalent seasonal influenza vaccine (Fluzone HD) in adults ≥65 years of age. The study will examine the impact of Fluzone HD on the immune response to mRNA-1345 against RSV-A and RSV-B, as well as the impact of mRNA-1345 on the immune response to Fluzone HD against 4 vaccine-matched Influenza A and B strains.

Timeline

Start

2023-09-25

Primary completion

2024-06-07

Completion

2024-06-07

Outcome

Mixed primary results

paper Noninferiority of immune responses against influenza A (H1N1, H3N2) and B (Austria, Phuket) was demonstrated PMID 42048601 ↗

paper Noninferiority against RSV-A and RSV-B based on GMR was not demonstrated; PMID 42048601 ↗

paper GMRs (95% CI) of neutralizing antibody were 0.625 (0.570-0.686) and 0.638 (0.584-0.697) for RSV-A and RSV-B, respectively, with the lower bound of 95% CI < 0.667 for RSV-A and B. PMID 42048601 ↗

Publications

• Comstock E, Fogarty C, Caso J, Vu J, Sinha A, Cao X, Chen H, Rushton L, Ma C, Priddy F. Coadministration of mRNA-1345 RSV vaccine with high-dose quadrivalent influenza vaccine in adults aged 65 and older: An observer-blinded, placebo-controlled, randomized, phase 3 trial. Hum Vaccin Immunother. 2026 Dec;22(1):2649335. doi: 10.1080/21645515.2026.2649335. Epub 2026 Apr 28.

Drugs

Evaluation	Drug	Modality	Dose	Route
Subject	Fluzone HD	Vaccine	—	Intramuscular
Subject	mRNA-1345	Messenger RNA (mRNA)	—	Intramuscular

Indications