The purpose of this Phase 2 study is to evaluate the safety and immunogenicity of an RSV-F protein nanoparticle vaccine, with aluminum, in 50 healthy third-trimester pregnant women and to assess the impact of maternal immunization on infant safety through one year of life.

Results

The Journal of Infectious Diseases published the results of this study on October 22, 2019.

Results: The vaccine was well tolerated; no meaningful differences in pregnancy or infant outcomes were observed between study groups. RSV-specific antibody levels increased significantly among vaccine recipients, including responses competitive with well-described monoclonal antibodies specific for multiple RSV neutralizing epitopes. No significant antibody increase was seen among placebo recipients, although a shallow upward trend across the RSV season was noted. Transplacental antibody transfer was 90%-120% across assays for infants of vaccinated women. Women with an interval of ≥30 days between vaccination and delivery demonstrated higher placental antibody transfer rates than women with an interval <30 days. Half-lives of RSV-specific antibodies in infants approximated 40 days. There was no evidence of severe RSV disease in infants of vaccinated mothers.

Conclusions: Data from this phase 2 study support a maternal immunization strategy to protect infants from RSV disease.