Efficacy and safety of respiratory syncytial virus prefusion F protein vaccine (RSVPreF3 OA) in older adults over 2 RSV seasons

Abstract

Background: The adjuvanted RSV prefusion F protein-based vaccine (RSVPreF3 OA) was efficacious against RSV-related lower respiratory tract disease (RSV-LRTD) in ≥60-year-olds over 1 RSV season. We evaluated efficacy and safety of 1 RSVPreF3 OA dose and of 2 RSVPreF3 OA doses given 1 year apart against RSV-LRTD over 2 RSV seasons post-dose 1.

Methods: In this phase 3, blinded trial, ≥60-year-olds were randomized (1:1) to receive RSVPreF3 OA or placebo pre-season 1. RSVPreF3 OA recipients were re-randomized (1:1) to receive a second RSVPreF3 OA dose (RSV_revaccination group) or placebo (RSV_1dose group) pre-season 2; participants who received placebo pre-season 1 received placebo pre-season 2 (placebo group). Efficacy of both vaccine regimens against RSV-LRTD was evaluated over 2 seasons combined (confirmatory secondary objective, success criterion: lower limits of 2-sided confidence intervals [CIs] around efficacy estimates >20%).

Results: The efficacy analysis comprised 24,967 participants (RSV_1dose: 6227, RSV_revaccination: 6242, placebo: 12,498). Median efficacy follow-up was 17.8 months. Efficacy over 2 seasons of 1 RSVPreF3 OA dose was 67.2% (97.5% CI: 48.2-80.0) against RSV-LRTD and 78.8% (95% CI: 52.6-92.0) against severe RSV-LRTD. Efficacy over 2 seasons of a first dose followed by revaccination was 67.1% (97.5% CI: 48.1-80.0) against RSV-LRTD and 78.8% (95% CI: 52.5-92.0) against severe RSV-LRTD. Reactogenicity/safety of the revaccination dose were similar to dose 1.

Conclusion: One RSVPreF3 OA dose was efficacious against RSV-LRTD over 2 RSV seasons in ≥60-year-olds. Revaccination 1 year post-dose 1 was well tolerated but did not seem to provide additional efficacy benefit in the overall study population. ClinicalTrials.gov registration: NCT04886596.

Keywords: RSV; older adults; respiratory syncytial virus prefusion F protein vaccine.