RSV_IMPACT Study 

Project Title

RSV_IMPACT Study: Maternal RSV Vaccination to Protect Infants

Overview

The RSV_IMPACT study is a Phase IV clinical trial evaluating the safety and effectiveness of an RSV (Respiratory Syncytial Virus) vaccine administered during pregnancy and its ability to protect infants from severe RSV-related respiratory illness in the first year of life. The study investigates whether maternal vaccination can reduce the risk of severe lower respiratory tract infection (LRTI) in newborns, while also carefully monitoring pregnancy and birth outcomes.

Rationale

Respiratory Syncytial Virus (RSV) is one of the leading causes of severe respiratory illness and hospitalisation in infants worldwide, particularly in the first six months of life. Although earlier clinical trials have shown that maternal RSV vaccination can provide meaningful protection to infants, important knowledge gaps remain—especially in African settings where RSV burden is high. This study was designed to:

• Confirm the real-world effectiveness of the RSV maternal vaccine (RSVpreF / Abrysvo™)
• Evaluate protection against severe RSV-associated illness in infants
• Assess potential safety signals, including preterm birth and other pregnancy outcomes
• Generate critical data from high-burden African populations, including South Africa

The findings will support evidence-based decisions on maternal RSV immunisation strategies globally.

Study Aim

To evaluate whether maternal RSV vaccination is safe during pregnancy and effective in preventing severe RSV disease in infants during their first 180 days of life.

Primary Objectives

• Assess vaccine efficacy against severe RSV-associated lower respiratory tract infection (LRTI) in infants up to 180 days of age
• Evaluate safety of the vaccine in pregnancy, including risk of preterm birth

Secondary Objectives

• Assess efficacy against RSV infection and hospitalisation in infants
• Evaluate all-cause respiratory illness outcomes
• Monitor maternal and infant safety outcomes, including low birth weight and very low birth weight
• Compare outcomes across HIV-exposed and HIV-unexposed infants
• Evaluate RSV subtype-specific protection (RSV-A and RSV-B)

Investigators

• Prof Lee Fairlie – Principal Investigator
• Dr Faeezah Patel – Sub-Investigator
• Dr Elizea Horne – Sub-Investigator
• Dr Mrinmayee Dhar – Sub-Investigator
• Dr Jeanne Coetzee – Sub-Investigator
• Tiffany Seef – Clinical Associate

Latest Update March 2026

For more about Pfizer RSV_IMPACT Study please email rhicomms@wrhi.ac.za