GlaxoSmithKline (GSK) has initiated dosing of patients in the Phase III clinical programme evaluating the safety and efficacy of its Respiratory Syncytial Virus (RSV) candidate vaccine for maternal immunisation (GSK3888550A).

The vaccine is made of recombinant subunit pre-fusion RSV antigen (RSVPreF3).

RSV is a major cause of respiratory infections, such as bronchiolitis and viral pneumonia in infants.

The latest study is followed by a positive Phase I/II safety, reactogenicity and immunogenicity data reported last month.

Data from this study in non-pregnant women showed that the candidate vaccine was well-tolerated and could rapidly boost the pre-existing immunity in the subjects leading to a high level of protecting neutralising antibodies.

The Phase III double-blind investiGational RSV mAternal vacCinE study (GRACE) will be conducted in up to 10,000 pregnant women aged between 18 and 49 years.

It will analyse the efficacy of a single dose of the RSV Maternal unadjuvanted candidate vaccine administered intramuscularly to the participants for the prevention of medically assessed RSV-associated LRTIs in their new-born infants.

In addition, the safety of the candidate vaccine both in vaccinated mothers and in their infants will be analysed.

GSK plans to conclude the study in early 2024 while the interim results will possibly be made available by the second half of 2022.

GlaxoSmithKline Vaccines R&D head and senior vice-president Emmanuel Hanon said: “RSV burden is high amongst young infants, a vaccine which protects them from birth would represent significant progress in addressing the burden of RSV, preventing infant illness and families’ distress, as well as reducing the associated burden for society.

“Advancing our portfolio of RSV vaccine candidates based on robust available data is a major step towards GSK’s goal of reducing the RSV-associated disease burden around the world.”