A bivalent respiratory synctial virus (RSV) A and B stabilized RSV prefusion F subunit vaccine is effective in reducing lower respiratory tract infection (LRTI) in older adults.

The interim analyses findings are part of a global phase 3, multicenter, randomized, double-blind, placebo-controlled clinical trial that includes up to 40,000 adults age 60 or older who are healthy or have stable chronic conditions.

The case accrual-based data were presented at IDWeek 2022, October 19-23, 2022, in Washington, DC, by Edward E. Walsh, MD, professor of medicine, University of Rochester.

Participants were randomly assigned to recieve either RSVpreF 120 µg (60 µg each of RSVpreF from RSV A and RSV B) or placebo. Overall, localized reactions were mild and included pain at vaccination site and some redness and swelling. Systemic symptoms were mild and indistiguishable between groups. Primary end points were number of cases with LRTI with ≥2 or ≥3 symptoms.

Through the first RSV season, 44 cases of LRTI with ≥2 symptoms were recorded, 11 of which were in the RSVpreF group and 33 in the placebo group, corresponding to 66.7% efficacy (96.66% CI, 28.8%-85.8%). Among those with LRTI ≥3 symptoms (n=16), 2 cases were in the RSVpreF group and 14 cases occurred in the placebo group, resulting in an efficacy of 85.7% (96.66% CI, 32.0%-98.7%). The vaccine was both safe and well-tolerated. Notably, symptoms of wheezing, shortness of breath, and tachypnea distinguished those with more severe LRTI.

An additional analysis among those with all respiratory infections (excluding LRTI; n=80), including 22 cases in the RSVpreF group and 58 cases in the placebo group, found that the RSVpreF vaccine was 62.1% effective at reducing all respiratory infections (95% CI, 37.1%-77.9%).

Notably, an analysis of data broken down by subgroups, including by age bracket and history of prespecified high-risk condition, demonstrated the vaccine’s efficacy across both symptom cohorts regardless of age or existing conditions.

The investigators plan to continue to assess efficacy through season 2 to assess duration of protection of RSVpreF.

For more coverage of IDWeek 2022, click here.

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