Pfizer announced in August 2022 that the Phase III clinical trial of RENOIR had demonstrated “positive top-line data”. RENOIR (RSV vaccine Efficacy iN Older adults Immunised against RSV disease) investigates Pfizer’s bivalent RSV prefusion F vaccine candidate, RSVpreF. This study looked into the administration of the candidate to adults over the age of 60.  


RSV disease is “characterised by several respiratory symptoms” and can be particularly dangerous for infants and older adults. Pfizer reported that an estimated “336,000 older adults are hospitalised globally due to RSV”. Furthermore, in the US, RSV infections in older adults “account for approximately 177,000 hospitalisations” with up to 14,000 deaths each year. There are currently “no prophylactic or therapeutic options” for older adults.  


The bivalent vaccine candidate comprises two preF proteins, selected to “optimise protection against RSV A and B strains”. It builds on “foundational basic science discoveries”. Among these is the detailed crystal structure of prefusion F, produced by the NIH. Prefusion F is a “key form of the viral fusion protein (F) that RSV uses to enter human cells”. Pfizer credits NIH research for demonstrating that “antibodies specific to the prefusion form” are “highly effective at blocking virus infection”. Following this, Pfizer tested “numerous” iterations of a stabilised prefusion F protein, eventually identifying a candidate that “elicited a strong anti-viral immune response in pre-clinical evaluations”.  

On top of the RENOIR programme, Pfizer revealed in March 2022 that RSVpreF received “Breakthrough Therapy Designation” from the FDA for the prevention of “RSV-associated lower respiratory tract disease caused by RSV” in infants up to 6 months old by “active immunisation of pregnant women”.  

The trial 

Pfizer described how a “pre-planned, interim analysis” of the efficacy of RSVpreF, conducted by an external Data Monitoring Company (DMC), assessed protection against “RSV-associated lower respiratory tract illness (LRTI-RSV)”. Following a “positive result” of vaccine efficacy (66.7%), Pfizer was able to explore the “more severe disease primary endpoint of LRTI-RSV”. Vaccine efficacy of 85.7% was observed, defined by “three or more symptoms”. The DMC also suggested that the vaccine was “well-tolerated, with no safety concerns”. Thus, Pfizer intends to submit a Biologics License Application (BLA) to the FDA.  

The RENOIR trial is a “global, randomised, double-bind, placebo-controlled study”. In August 2022 it had already enrolled around 37,000 participants. Participation will increase in the Southern Hemisphere to “accumulate cases during their first season”.  

Dr Annaliesa Anderson, Senior Vice President and Chief Scientific Office, Vaccine Research and Development, said that Pfizer is “delighted” at this progress.  

“Scientists and researchers have worked to develop RSV vaccines with little success for over half a century.” 

She believes that these findings are an “important step” in the effort against RSV. Pfizer is prepared to work with the FDA and “other regulatory agencies” to ensure the vaccine is “available to help address the substantial burden of RSV”.  

To hear more about vaccines against RSV come to the World Vaccine Congress in Europe, 2022.