Pfizer has reported positive top-line findings from the Phase III RENOIR clinical trial of its bivalent respiratory syncytial virus (RSV) prefusion F vaccine candidate, RSVpreF, in adults aged 60 years or above. 

The vaccine comprises two preF proteins chosen to enhance protection against RSV A and B strains.

The randomised, international, double-blind, placebo-controlled trial is designed to assess the safety, efficacy, and immunogenicity of one dose of the vaccine in adults aged 60 years and above. 

It has enrolled nearly 37,000 subjects so far, who are categorised into a 1:1 ratio to receive 120μg RSVpreF or a placebo. 

Enrolment of up to nearly 40,000 subjects is currently underway in the Southern Hemisphere.

According to findings from an independent, external Data Monitoring Committee (DMC)-conducted interim assessment of RSVpreF, the vaccine showed an efficacy of 66.7%. 

The analysis evaluated protection offered by the vaccine against lower respiratory tract illness linked to RSV (LRTI-RSV) that were defined by two or more symptoms.

On a primary endpoint of LRTI-RSV defined by three or more symptoms, the vaccine had a 85.7% efficacy. 

The DMC also noted that the RSVpreF vaccine was found to be well-tolerated, without any safety concerns. 

With the positive data, the company anticipates filing a Biologics License Application (BLA) for the vaccine with the US Food and Drug Administration (FDA), as well as with other agencies soon.

Pfizer Vaccine Research and Development senior vice-president and chief scientific officer Annaliesa Anderson said: “We are delighted that this first bivalent RSV vaccine candidate, RSVpreF, was observed to be efficacious in our clinical trial against this disease, which is associated with high levels of morbidity and mortality in older adults. 

“These findings are an important step in our effort to help protect against RSV disease, and we look forward to working with the FDA, and other regulatory agencies, to make this vaccine candidate available to help address the substantial burden of RSV disease in older adults.”

In July this year, Pfizer and BioNTech began a Phase II trial of an ‘enhanced’ Covid-19 mRNA-based vaccine candidate, BNT162b5.