The following is a summary of “Safety and Immunogenicity of an mRNA-Based RSV Vaccine Including a 12-Month Booster in a Phase I Clinical Trial in Healthy Older Adults,” published in the February 2024 issue of Infectious Diseases by Shaw et al.

Researchers conducted a retrospective study to investigate mRNA-1345, an mRNA-based RSV vaccine, to mitigate the RSV disease burden among elderly individuals through clinical trials.

They conducted a phase 1 trial, employing randomization and blinding, to assess the safety, reactogenicity, and immunogenicity of mRNA-1345 in adults aged 65-79 years. Participants were randomly assigned to receive a single dose of mRNA-1345 (at doses of 12.5, 25, 50, 100, or 200 µg) or placebo, with subsequent administration of a matched mRNA-1345 booster or placebo after 12 months.

The results showed that of the 298 participants, 247 received the booster injection at 12 months. Following both injections, mRNA-1345 demonstrated generally favorable tolerability, with commonly reported solicited adverse reactions, including injection-site pain, fatigue, headache, arthralgia, and myalgia. Reactogenicity was more pronounced after the booster injection but exhibited similar severity, onset time, and duration compared to the initial injection. A single dose of mRNA-1345 significantly elevated RSV-A and RSV-B neutralizing antibody titers (nAb) as well as prefusion-F-binding antibody (preF-bAb) concentrations at the one-month mark (geometric mean-fold rises: RSV-A, 10.2-16.5; RSV-B, 5.3-12.5; preF-bAb, 7.2-12.1). These elevated RSV antibody levels persisted above baseline for 12 months, indicating a sustained immune response. Administration of the booster injection at 12 months resulted in increased RSV-A and RSV-B nAb titers and preF-bAb concentrations; however, the post-booster titers were numerically lower compared to those observed after the initial dose, with overlapping 95% CIs.

Investigators concluded that mRNA-1345, a single-shot RSV vaccine with a 12-month booster, demonstrated good safety and immune response, supporting its further development.

Source: academic.oup.com/jid/advance-article/doi/10.1093/infdis/jiae081/7612559