Safety and Immunogenicity of a Respiratory Syncytial Virus Fusion (F) Protein Nanoparticle Vaccine in Healthy Third-Trimester Pregnant Women and Their Infants

J Infect Dis. 2019 Oct 22;220(11):1802-1815. doi: 10.1093/infdis/jiz390.


Background: Respiratory syncytial virus (RSV) is the leading cause of infant lower respiratory tract disease and hospitalization worldwide.

Methods: Safety and immunogenicity of RSV fusion (F) protein nanoparticle vaccine or placebo were evaluated in 50 healthy third-trimester pregnant women. Assessments included vaccine tolerability and safety in women and infants, and RSV-specific antibody measures in women before and after vaccination, at delivery and post partum.

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.

Clinical trials registration: NCT02247726.

Keywords: infant; maternal immunization; pregnancy; respiratory syncytial virus (RSV); vaccine.

Publication types

  • Clinical Trial, Phase II
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Antibodies, Viral / blood
  • Drug-Related Side Effects and Adverse Reactions / epidemiology
  • Drug-Related Side Effects and Adverse Reactions / pathology
  • Female
  • Healthy Volunteers
  • Humans
  • Infant
  • Male
  • Placebos / administration & dosage
  • Pregnancy
  • Pregnancy Trimester, Third
  • Respiratory Syncytial Virus Infections / prevention & control*
  • Respiratory Syncytial Virus Vaccines / administration & dosage
  • Respiratory Syncytial Virus Vaccines / adverse effects*
  • Respiratory Syncytial Virus Vaccines / immunology*
  • Vaccines, Virus-Like Particle / administration & dosage
  • Vaccines, Virus-Like Particle / adverse effects*
  • Vaccines, Virus-Like Particle / immunology*
  • Viral Fusion Proteins / immunology*
  • Young Adult


  • Antibodies, Viral
  • F protein, human respiratory syncytial virus
  • Placebos
  • Respiratory Syncytial Virus Vaccines
  • Vaccines, Virus-Like Particle
  • Viral Fusion Proteins

Associated data