A New Weapon Against RSV

On 10 December 2024, Moderna announced final Phase III results for mRNA-1345, its investigational vaccine targeting respiratory syncytial virus (RSV) in older adults. The vaccine, built on the same mRNA platform as Moderna’s COVID-19 shot, achieved 83% efficacy against RSV-associated lower respiratory tract disease in adults aged 60 and older.

RSV is a major cause of hospitalization and mortality in older populations, yet vaccine options remain limited. Moderna’s success adds momentum to the mRNA vaccine revolution, expanding its reach beyond pandemic response.

Trial Design and Key Findings

The randomized, placebo-controlled trial enrolled over 35,000 participants across North America and Europe. Key outcomes included:

• 83% efficacy against RSV-associated lower respiratory tract illness
• Strong immunogenicity with robust neutralizing antibody responses
• Favourable safety profile, with mild injection site reactions and fatigue as the most common side effects
• No cases of myocarditis or serious adverse events linked to the vaccine

The trial met all primary and secondary endpoints, and Moderna plans to submit for FDA and EMA approval in early 2025.

Implications for Public Health

If approved, mRNA-1345 would become the first mRNA-based RSV vaccine for older adults, joining GSK and Pfizer’s protein-based RSV vaccines in a rapidly evolving market. Its scalable manufacturing and rapid adaptability could prove critical in seasonal outbreaks and future respiratory pandemics.

Moderna is also testing mRNA-1345 in paediatric and immunocompromised populations, and exploring combination vaccines for RSV, influenza, and COVID-19.