1. In this randomized-controlled trial, an mRNA-based vaccine was efficacious at preventing symptomatic infection with respiratory syncytial virus (RSV) involving one respiratory sign or symptom in 68.4% of participants.
2. The mRNA-based vaccine was associated with a higher rate of mild to moderate adverse events than placebo.
Evidence Rating Level: 1 (Excellent)
Study Rundown: RSV is associated with a high incidence of morbidity and mortality globally, particularly for older adults for the phenomenon of immunosenescence and a higher baseline rate of concomitant medical comorbidities. With recent advancements in mRNA-based vaccines, the potential for similar applications towards developing an mRNA-based vaccine for RSV has been promising. This was an international randomized controlled study evaluating the efficacy and safety of an mRNA-based vaccine against RSV developed by Moderna amongst non-immunocompromised adults older than 60 years old. Results of the analysis found that the mRNA vaccine against RSV was efficacious at preventing symptomatic infection within at least one sign or symptom in 68.4% of participants, 83.7% efficacious against symptomatic infection with at least two signs or symptoms, and 82.4% efficacious against symptomatic infection with three or more signs or symptoms. The mRNA vaccine was found to be associated with a higher incidence of both systemic and local adverse events. However, the majority of these reactions were mild or moderate. A key limitation to note of this study is that results cannot be generalized to older adults who are immunocompromised. Further, the effectiveness of the vaccine outside trial conditions is unclear. In summary, the trial provided evidence that the Moderna mRNA vaccine against RSV is efficacious at reducing the incidence of symptomatic infection with RSV amongst non-immunocompromised adults older than 60 years old.
Click here to read the study in NEJM
In-Depth [randomized controlled trial]: This was a Moderna-sponsored international randomized controlled phase 2-3 trial investigating the safety and efficacy of a single dose of mRNA-1345 in the prevention of RSV-associated respiratory tract disease when compared to a placebo amongst adults older than 60 years old. The primary outcome of interest was the prevention of moderate-to-serious RSV symptoms as measured by two or three respiratory signs or symptoms and the prevention of at least one RSV symptom between 14 days to 12 months after receiving the vaccine. Adults meeting the age criteria with select stable chronic medical conditions were included in the study. Adults who were immunocompromised were excluded from the study. Overall, 35,541 participants were randomized in a 1:1 ratio to receive 50μg of the mRNA-1345 vaccine (n=17,793) or placebo (n=17,748). Results of the primary analysis found that the mRNA-1345 vaccine was 83.7% efficacious against infection with two signs or symptoms and 82.4% efficacious at preventing infection with three or more symptoms. However, the mRNA-1345 vaccine group demonstrated a higher incidence of solicited local and systemic adverse reactions as compared to placebo. Overall, this study provided evidence that the mRNA-1345 vaccine was not associated with significant safety concerns beyond what has previously been reported. Further, this study supports the hypothesis that the mRNA-1345 vaccine may be beneficial for select individuals to prevent symptomatic infection with RSV.
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