The long-acting monoclonal antibody nirsevimab may be more effective in protecting infants against respiratory syncytial virus than clinical trial results would suggest, according to a real-world study.

The US Centers for Disease Control and Prevention (CDC) report showed that passive immunisation with nirsevimab (Beyfortus) was 90% effective in preventing respiratory syncytial virus (RSV)-related hospitalisations in infants versus an 81% efficacy rate seen in phase III trials.

This early estimate demonstrated that “receipt of a single dose of nirsevimab was highly effective against RSV-associated hospitalisation in infants entering their first RSV season”, the authors wrote.

It comes a week after the WA Government announced an $11 million statewide rollout of nirsevimab ahead of winter.