August 24, 2015
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RSV F vaccine safe, well-tolerated in women of childbearing age

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In women aged 18 to 35 years, a candidate recombinant respiratory syncytial virus fusion vaccine was safe and induced an immune response protective against the virus, according to results of a phase 2 randomized controlled trial.

Pedro A. Piedra, MD, professor in the department of molecular virology and microbiology and the department of pediatrics at Baylor College of Medicine, and colleagues randomly assigned 330 healthy, nonpregnant women to one of nine formulations of a candidate respiratory syncytial virus recombinant F nanoparticle vaccine (RSV F) or placebo. Participants were assigned a single- or two-dose injection regimen that contained 60 µg or 90 µg of the vaccine; some doses also contained 1.2 mg aluminum phosphate, the researchers wrote. The study was conducted at four sites in the United States.

Pedro Piedra

Pedro A. Piedra

Piedra and colleagues evaluated the safety of the vaccine during a 180-day period that spanned an entire RSV season. In addition, the researchers assessed immunogenicity and RSV infection rates over 112 days.

Overall, the vaccine formulations were well-tolerated; no patients reported any vaccine-related serious adverse events. The most common adverse events primarily were mild to moderate pain at injection sites. As for systemic reactions, the most common adverse events were headache, fatigue, muscle pain, nausea and chills.

All vaccine formulations, with or without aluminum adjuvant, promoted an immune response, the researchers said. Anti-F immunoglobulin G antibody responses were detected as early as 7 days post-vaccination and peaked at 28 days after the first or second dose. These levels also persisted through 112 days after vaccination. Anti-F IgG levels rose 6.5-fold to 15.6-fold across all doses; however, levels were significantly higher in the two-dose, aluminum-adjuvanted regimens at day 56.

Synagis (palivizumab, MedImmune)-competitive antibody levels rose to 325 µg/mL by day 56, according to Piedra and colleagues.

“In the current study, the different formulations of the candidate RSV recombinant F nanoparticle vaccine were well-tolerated in healthy women of childbearing age, and induced immune responses that may be consistent with protection against RSV disease,” they wrote. “The study confirmed the value of a higher antigen dose, the increased immunity with aluminum phosphate and the potential for a single-dose vaccine.” – by Colleen Owens

 Disclosure: Piedra reports being a consultant to and receiving financial support from Novavax All other authors report being salaried employees of Novavax and holding stock options.