Moderna’s mRNA Vaccine Candidate Prevents RSV-Associated Disease in Older Adults

Topline results were announced from a phase 3 study evaluating Moderna’s investigational mRNA vaccine candidate, mRNA-1345, for the prevention of respiratory syncytial virus-associated lower respiratory tract disease (RSV-LRTD) in older adults.

The double-blind, placebo-controlled ConquerRSV trial ( Identifier: NCT05127434) enrolled approximately 37,000 adults 60 years of age and older. Participants were randomly assigned to receive a single dose of mRNA-1345 or placebo. The primary endpoint was vaccine efficacy, defined as the prevention of the first episode of RSV-LRTD with 2 or more symptoms, or with 3 or more symptoms, from 14 days post vaccination through 12 months.

Results showed vaccine efficacy of 83.7% (95% CI, 66.1-92.2; P <.0001) against RSV-LRTD, defined by 2 or more symptoms. There were 64 cases of RSV-LRTD with 2 or more symptoms reported in the interim analysis; 55 of these cases occurred in the placebo group while 9 occurred in the mRNA-1345 group. 

Vaccine efficacy against RSV-LRTD with 3 or more symptoms was reported to be 82.4% (96.36% CI, 34.8-95.3; P =.0078). Among the 20 cases of RSV-LRTD with 3 or more symptoms, 17 cases were observed in the placebo group and 3 cases were observed in the mRNA-1345 group.

The most commonly reported adverse reactions were injection site pain, fatigue, headache, myalgia, and arthralgia. The vaccine candidate was generally found to be well tolerated; no safety concerns were identified.

Based on these results, the Company intends to submit for regulatory approval in the first half of 2023.


Moderna announces mRNA-1345, an investigational respiratory syncytial virus (RSV) vaccine, has met primary efficacy endpoints in phase 3 trial in older adults. News release. Moderna. Accessed January 18, 2023.

This article originally appeared on MPR