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Positive Data Reported for RSV Vaccine in Women of Childbearing Age

Mid-stage trial shows increase in antibody levels

Positive safety and immunogenicity data have been reported from a randomized, blinded, placebo-controlled phase II study designed to evaluate the immunogenicity and safety of multiple formulations of a respiratory syncytial virus (RSV)-F protein nanoparticle vaccine adjuvanted with aluminum phosphate in women of childbearing age. The treatment is being developed by Novavax.

The study’s primary outcomes were the safety of and immune responses to the RSV-F vaccine candidate. Immune responses were measured by levels of serum immunoglobulin G antibody specific for the F protein. The trial enrolled 720 healthy women between the ages of 18 and 35 years, who received one or two intramuscular injections of different dose levels of vaccine antigen with a range of doses of aluminum phosphate adjuvant.

The new data reflect the vaccine’s safety and immunogenicity over a 91-day period after the first immunization. Study highlights include the following:

  • The RSV-F vaccine candidate was well-tolerated, with no vaccine-related serious adverse events, at all doses and formulations.
  • Significant increases in RSV-F antibody levels were observed across all doses and formulations. Peak RSV-F antibody levels were observed in the group that received a single dose of vaccine containing 120 mcg of antigen with one-third of the aluminum phosphate dose used in prior studies.
  • Clear increases in RSV-neutralizing antibodies were also shown across all doses and formulations, and were strongest in women entering the study with the lowest baseline levels.
  • Vaccine-induced palivizumab-like antibody levels demonstrated strong concordance with anti–RSV-F antibody responses. A single 120-mcg antigen dose generated peak palivizumab-like antibody levels of approximately 400 mcg/mL.
  • A kinetic analysis of the antibody responses showed rapid increases in antibody levels with all vaccine formulations and dosing regimens. A single 120-mcg antigen dose generated peak RSV-F and palivizumab-like antibody levels within 14 days of immunization, and high levels of both were sustained through the 91-day observation period.

RSV is a respiratory pathogen that affects all humans regardless of age. In healthy adults, RSV infections are generally mild-to-moderate in severity, but may be more severe in infants and young children as well as in the elderly and in adults with underlying chronic cardiac or pulmonary disease.

Globally, RSV is a common cause of childhood respiratory infection, with a disease burden of 64 million cases and approximately 160,000 deaths annually. Severe RSV disease results in 3.4 million hospital admissions per year globally and disproportionately affects infants younger than 6 months of age.

It is estimated that between 11,000 and 17,000 elderly and high-risk adults die of RSV infection annually in the U.S., with up to 180,000 hospitalizations for serious respiratory symptoms. Currently, no approved RSV prophylactic vaccines are available for either of these populations.

Source: Novavax; April 28, 2014.

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