Pfizer has unveiled the top-line positive efficacy and safety data for its Abrysvo vaccine in preventing respiratory syncytial virus (RSV) in older adults aged 60 years and above.

The US drugmaker announced the data from the ongoing Phase 3 RENOIR (RSV vaccine Efficacy study iNOlder adults Immunized against RSV disease) clinical trial.

RSV is a contagious virus that can affect the lungs of a person and can potentially cause severe illness in young infants, older adults, and individuals with certain chronic medical conditions.

Abrysvo is a bivalent vaccine, designed to protect against all RSV-related lower respiratory tract disease (LRTD), defined by three or more symptoms, regardless of the virus subgroup.

Pfizer said that currently, it is the only company providing an RSV vaccine to help protect older adults, along with infants through maternal immunisation.

In the study, the vaccine showed 77.8% efficacy against RSV-associated LRTD after disease surveillance in season two, and 88.9% efficacy after season one, which indicates a durable efficacy after two seasons.

Abrysvo also showed a consistent vaccine efficacy for both RSV A and RSV B after season two with more than 80% vaccine efficacy against each subtype for LRTD.

The vaccine efficacy was also sustained against less severe LRTD, defined by two or more symptoms, from 65.1% after season one to 55.7% after the end of season two.

In the study, the vaccine showed 81.5% efficacy against RSV-associated LRTD across both seasons after 16.4 months of disease surveillance.

Also, no new adverse events were reported through the second RSV season, apart from what was reported in the clinical trial during the first season.

The US drugmaker intends to submit the data to regulatory authorities and vaccine technical committees and is also planning to publish the findings in a peer-reviewed scientific journal.

Pfizer vaccine research and development senior vice president and chief scientific officer Annaliesa Anderson said: “We are encouraged by the level of protection that we observed after two full RSV seasons for Abrysvo.

“This new data indicate that broad and durable protection against both types of RSV that cause disease, RSV A and RSV B, is the potential benefit to having a bivalent vaccine.”

In May last year, the US Food and Drug Administration (FDA) approved Abrysvo for the prevention of LRTD caused by RSV in individuals aged 60 years and above.

In August, the vaccine was approved in both the US and Europe, for the prevention of LRTD and severe LRTD caused by RSV in newborns up to six-month-olds, through active immunisation of pregnant women.