Administration of a respiratory syncytial virus (RSV) fusion (F) protein nanoparticle vaccine in healthy women aged 18 to 35 years was both well tolerated as well as immunogenic.

• Randomized, observer-blind, placebo-controlled, phase 2 study evaluated the immunogenicity and safety of different formulations of RSV F vaccine in both 1- and 2-dose schedules
• “Placebo, or vaccine with 60g or 120g of RSV F protein and 0.2, 0.4, or 0.8 mg aluminum, were administered intramuscularly on Days 0 and 28 to healthy women 18-35 years old”
• Immunogenicity was evaluated Days 0 to 91 by assessing anti-F IgG and palivizumab-competitive antibody (PCA) measurements obtained using ELISA, and RSV A and B neutralizing antibodies measured using a microneutralization (MN) assay
• Solicited and unsolicited adverse events were collected (obtained through Day 7 and 91, respectively)

• All vaccine formulations were well-tolerated
• No treatment-related adverse events were reported
• Increased anti-F IgG and PCA responses seen after both doses; increased MN after the first dose only
• “The timeliest and most robust antibody responses followed one dose of 120g RSV F protein and 0.4mg aluminum, but persistence through 91 days was modestly (~25%) superior following two doses of 60g RSV F protein and 0.8mg aluminum”
• Analysis by Western bolt showed a 52% reduction in RSV infections in active vaccines during the Day 0 to 90 period (p=0.009 overall)