• Geert Leroux-Roels, Fien De Boever, Cathy Maes, Thi Lien-Anh Nguyen, Sherryl Baker, and Antonio Gonzalez Lopez.
• Centre for Vaccinology, Ghent University Hospital, C. Heymanslaan 10, 9000 Ghent, Belgium. Electronic address: Geert.LerouxRoels@UGent.be.
• Vaccine. 2019 May 6; 37 (20): 2694-2703.

IntroductionRespiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infections in infants. An investigational vaccine using an engineered recombinant RSV fusion glycoprotein in its post-fusion conformation (RSV F subunit vaccine) has been developed to protect young infants via maternal immunization. This first-in-human, phase I, observer-blind study (NCT02298179) evaluated the safety and immunogenicity of different dosages and formulations of RSV F subunit vaccine in healthy non-pregnant women and men aged 18-45 years.MethodsParticipants were enrolled (1:1:1) in a stepwise dosage-escalation manner into three cohorts to receive RSV F subunit vaccine containing 45 µg, 90 µg and 135 μg of RSV F glycoprotein. Within each cohort, participants were randomized (1:1:1:1) to receive two doses of RSV F subunit vaccine with (aluminum hydroxide or MF59) or without adjuvant, or placebo, ≥28 days apart. Safety (until day 365 post-dose 2), anti-RSV neutralizing antibodies (NAbs) and serum total binding antibodies to RSV F protein (until day 181 post-dose 1) were evaluated.ResultsAll formulations were well-tolerated. No vaccine-related serious adverse events were reported. All participants were seropositive for anti-RSV NAbs at baseline, with geometric mean titers (GMTs) ranging from 184 (95% confidence interval [CI]: 127-266) to 380 (95% CI: 272-531). At 28 days post-dose 1, anti-RSV NAb GMTs in vaccine recipients ranged from 893 (95% CI: 702-1,136) to 1,602 (95% CI: 1,243-2,064). No booster effect was observed, but immune responses were maintained above pre-vaccination levels for six months post-dose 1. Ratios of RSV F total binding antibodies fold changes to NAb fold changes ranged from 2.79 to 4.12 at 28 days post-dose 1. The impact of the adjuvant was limited.ConclusionsA single dose of each formulation of RSV subunit F vaccine was well-tolerated and enhanced preexisting NAb titers through six months of follow-up.Copyright © 2019 GlaxoSmithKline Biologicals SA. Published by Elsevier Ltd.. All rights reserved.

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