Pfizer RSV Vaccine Study In HIV-Infected Pregnant Woman

A Phase 3 trial has been initiated as a randomized, double-blinded, placebo-controlled study to assess the safety, tolerability, and immunogenicity of the Respiratory Syncytial Virus (RSV) Prefusion F Subunit Vaccine in pregnant participants living with HIV and their infants. Maternal immunization stands as a promising strategy for preventing infant diseases.


Previous Phase 1/2 studies conducted in healthy nonpregnant adults and a pivotal Phase 3 study involving pregnant participants have demonstrated the RSVpreF vaccine’s acceptable tolerability and safety. Notably, robust immune responses were observed one month post-vaccination in the Phase 1/2 studies. The combined RSV A and B serum neutralization geometric mean titers (GMTs) achieved were notably higher, ranging from 12 to 20 times, compared to a concentration of 100 µg/mL of palivizumab, a monoclonal antibody known for near-complete protection against severe RSV disease in high-risk infants. Pfizer’s Phase 3 study in healthy pregnant participants showed that RSVpreF met the pre-specified efficacy criteria for preventing medically attended lower respiratory tract infections (MA-LRTI) in infants.

Globally, nearly 1000 women are newly infected with HIV daily, although widespread access to antiretroviral therapy (ART) has decreased vertical HIV transmission rates. HIV-exposed but uninfected infants face higher morbidity and mortality rates from RSV infection compared to their HIV-unexposed counterparts, potentially due to reduced transplacental transfer of maternal antibodies. This randomized, double-blinded, placebo-controlled study aims to evaluate Pfizer’s RSVpreF in a cohort of HIV-infected pregnant participants to assess the vaccine’s safety, tolerability, and immunogenicity in the context of maternal HIV infection.

The evaluation of RSVpreF in this population is crucial due to the added burden of HIV infection on infant RSV disease globally. Studies have shown reduced transplacental transfer of RSV-neutralizing antibodies in newborns born to HIV-infected pregnant women, with some mitigation observed with maternal viral suppression, use of combination ART, and absence of hypergammaglobulinemia, although data is limited. Maternal HIV infection has also been linked to diminished immune responses and disease protection following maternal influenza vaccination. Descriptive immunogenicity studies will help clarify potential attenuating effects of HIV infection on immune responses to RSVpreF.


  • Dr Elizea Horne (Principal Investigator)
  • Prof Lee Fairlie (Sub-Investigator)
  • Dr Faeezah Patel (Sub-Investigator)
  • Dr Mrinmayee Dhar (Sub-Investigator)
  • Dr Muneerah Khan (Sub-Investigator)
  • Dr Jeanne Coetzee (Sub-Investigator)
  • Tiffany Seef (Clinical Associate)
  • Othusitse Segalo (Clinical Associate)

Latest Update

March 2024

For more about Pfizer RSV Vaccine Study please email

Stay up to date

Get updates on news, resources, events and happenings from Wits RHI.