RSVpreF (or PF-06928316) is a bivalent RSV prefusion vaccine candidate (RSV A and B) which reported 81.1% vaccine efficacy in Phase 3 trials against sever lower respiratory tract illness in infants in the first 90 days of life.
Respiratory Syncytial Virus – a contagious virus and common cause of respiratory illness – accounts for around 2.1 million outpatient visits and 58,000 hospitalizations a year among children under five.
Worldwide, RSV results in the death of approximately 102,000 children annually, with about half of those in infants less than six months old and the vast majority in developing countries.
In November, the Pan American Health Organization warned of a ‘triple threat’ of RSV, COVID-19 & seasonal influenza infections: noting that RSV infections had increased significantly in countries including the US, Canada, Mexico & Brazil.
The European Centre for Disease Control and Prevention made a similar observation in December: noting a very early rise in seasonal infections.
“If approved, RSVpreF would help protect infants at their first breath from the devastating effects of this infectious disease, which though well-known, has been particularly evident throughout this RSV season,” said Annaliesa Anderson, Ph.D., Senior Vice President and Chief Scientific Officer, Vaccine Research & Development, Pfizer.
“We look forward to progressing the review of Pfizer’s RSV maternal vaccine candidate with the FDA and other regulatory authorities, given its significant potential to positively contribute to global health in the prevention of RSV in infants.”
The European Medicines Agency (EMA) has also accepted Pfizer’s marketing authorization application (MAA) under accelerated assessment for both older adult and maternal RSV vaccines: with a decision expected in the second half of 2023.
Competition heats up
Pfizer is already expecting a decision from the FDA on its RSV vaccine for older adults in May: while several other late-stage candidates are hoping to be among the first vaccines on the market for the indication (GSK is expecting a decision the same month; while Moderna is due to file for regulatory approval for its mRNA vaccine within the first half of the year).
But Pfizer highlights it is the only company with a maternal RSV vaccine in late-stage development (GSK put a hold on its Phase 3 maternal vaccine trial in February last year).
Meanwhile, AstraZeneca and Sanofi are also expecting a decision from the FDA on antibody nirsevimab - for the prevention of RSV lower respiratory tract disease in newborns and infants - in the third quarter of this year (the drug was granted marketing authorization in the EU as Beyfortus in November).
Pfizer's maternal immunization regulatory submission is supported by its Matisse (MATernal Immunization Study for Safety and Efficacy) Phase 3 clinical trial evaluating the efficacy, safety, and immunogenicity of RSVpreF against medically attended lower respiratory tract illness (MA-LRTI) and severe MA-LRTI in infants born to healthy women vaccinated during pregnancy.
Vaccine efficacy of 81.8% was observed against severe medically attended lower respiratory tract illness due to RSV in infants from birth through the first 90 days of life with high efficacy of 69.4% demonstrated through the first six months of life.
The global study covered 18 countries and started in June 2020, spanning multiple RSV seasons in both the northern and southern hemisphere.