Moderna Will Have to Wait for FDA Approval of Investigational RSV Vaccine

While Moderna expects mRNA-1345 to be approved later this month, the company cites FDA administrative constraints as reason for delay.

The US Food and Drug Administration (FDA) will not complete its review of the Biologics License Application (BLA) for Moderna’s investigational mRNA-1345 vaccine by the previously communicated Prescription Drug User Fee Act date of May 12, 2024, according to a Moderna press release.1

According to Moderna officials, the FDA cited administrative constraints for the reason behind the delay of the review for Moderna’s investigational respiratory syncytial virus (RSV) vaccine. The agency did indicate that it expects to conclude the review of the BLA by the end of May 2024. The FDA also did not inform the manufacturer of any issues related to vaccine safety, efficacy, or quality that would prevent the approval of mRNA-1345.1

Moderna noted in the press statement that they still anticipate that the US CDC Advisory Committee on Immunization Practices (ACIP) will include mRNA-1345 on the agenda of its June 26-28 meeting. "Moderna is very grateful to the FDA for their continued efforts and diligence," Stephen Hoge, MD, President of Moderna, said in the release. "We look forward to helping the agency complete the review of our application, and to the June ACIP meeting."1

For the approval, the FDA will be reviewing findings from ConquerRSV, a randomized, double-blind, placebo-controlled trial that included 35 541 adults aged 60 years and older conducted across 22 countries. The dual primary efficacy endpoints were based on 2 definitions of RSV lower respiratory tract disease (RSV-LRTD)—RSV-LRTD with 2 or more symptoms and RSV-LRTD with 3 or more symptoms of disease. Participants were randomly assigned to receive a single dose of the investigational vaccine or placebo.2

Based on analyses conducted when at least half of the anticipated cases of RSV-LRTD had occurred, vaccine efficacy was 83.7% against the disease with at least 2 signs or symptoms and 82.4% effective against RSV-LRTD with at least 3 signs or symptoms.2 Conquer-RSV investigators reported vaccine efficacy against RSV-associated acute respiratory disease of 68.4%.2 The phase 3 trial, published in the New England Journal of Medicine in December 2023, also found equal protection against RSV subtypes A and B.2

Local and systemic adverse reactions were more common among participants in the active vaccine group compared to the placebo group, although most were transient and mild to moderate in severity. In both groups, 2.8% of participants experienced severe adverse events.2

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