A Phase 2/3, Randomized, Observer-Blind, Placebo-Controlled Study to Evaluate the Safety and Efficacy of mRNA-1345, an mRNA Vaccine Targeting Respiratory Syncytial Virus (RSV), in Adults ≥60 Years of Age

mRNA-1345-P301

The main purpose of Part A of this study is to evaluate the safety and tolerability of mRNA-1345 vaccine and to demonstrate the efficacy of a single dose of mRNA-1345 vaccine in the prevention of a first episode of RSV-associated lower respiratory tract disease (RSV-LRTD) as compared with placebo from 14 days postinjection through 12 months. The main purpose of Part B of this study is to evaluate the safety, tolerability and immunogenicity of a booster dose (BD) of mRNA-1345 administered 24 months after the primary dose.

2021-11-17

2025-08-25

2025-08-25

Active (not recruiting)

Early phase I

36557

Key Inclusion Criteria (Part A): * Adults ≥ 60 years of age who are primarily responsible for self-care and activities of daily living. Participants may have one or more chronic medical diagnoses (including chronic heart failure \[CHF\] and chronic obstructive pulmonary disease \[COPD\]), but should be medically stable * Body mass index from ≥18 kilograms (kg)/square meter (m\^2) to ≤35 kg/m\^2 Key Inclusion Criteria (Part B): * Randomized to and were subsequently vaccinated with the mRNA-1345 study injection in Part A at least 21 months prior to Screening. Key Exclusion Criteria (Part A): * Participation in another clinical research study where participant has received an investigational product (drug/biologic/device) within 6 months before the planned date of the Day 1 study injection. * Current participation in research involving receipt of any investigational RSV product * History of a serious reaction to any prior vaccination or Guillain-Barré syndrome within 6 weeks of any prior influenza immunization. * Received or plans to receive any non-study vaccine within 28 days before or after the Day 1 study injection. Key Exclusion Criteria (Part B): * Participation in another clinical research study where participant has received an investigational product (drug/biologic/device) within 6 months before the planned date of BD study injection (BD Day 1). * History of a serious reaction to any prior vaccination, or Guillain-Barré syndrome within 6 weeks of any prior influenza immunization. * Received or plans to receive any non-study vaccine (including authorized or approved vaccines for the prevention of coronavirus disease 2019 (COVID-19) regardless of type of vaccine) within 14 days before or after the BD Day 1 study injection. * Received or plans to receive any commercial RSV vaccination at any time prior to BD study injection (BD Day 1) or during the substudy. Other inclusion and/or exclusion criteria may apply.

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2024-02-09