Daijiworld Media Network - New Delhi

New Delhi, Jun 5: A single injection of nirsevimab, a long-acting monoclonal antibody developed to prevent respiratory syncytial virus (RSV) infections in infants, can significantly reduce hospitalisations for bronchiolitis, according to a new study.

Bronchiolitis is a common and sometimes severe respiratory illness affecting children under one year of age, especially in the first six months, with cases peaking between November and March. RSV is the most frequent culprit, responsible for roughly three out of every four cases, and can cause respiratory failure in severe instances.

In a first-of-its-kind real-world study, researchers evaluated the actual impact of nirsevimab across different European countries, including Spain, the UK, and Italy, each with distinct health policies.

Data collected from 68 hospitals in Catalonia (Spain) and five in the UK and Italy revealed a striking result: in Catalonia, where nirsevimab was administered, hospital admissions for bronchiolitis in infants under six months nearly halved compared to previous seasons. Emergency room visits for bronchiolitis also saw a marked decline in the same age group. By contrast, countries where nirsevimab was not deployed showed no significant reduction.

“This study represents a key milestone in understanding how new prevention strategies can tackle RSV,” said Danilo Buonsenso, a researcher in General and Specialist Paediatrics at the Catholic University of the Sacred Heart in Rome. “For the first time, we’re comparing countries with different policies to evaluate real-world effectiveness.”

The research, published in The Lancet Regional Health – Europe, also noted that the protective effect of nirsevimab was strongest in babies under six months old, with a less pronounced impact in children aged six to 23 months.

In May, the World Health Organization (WHO) recommended the use of nirsevimab alongside a maternal vaccine (RSVpreF) to help protect newborns from RSV, the leading cause of lower respiratory tract infections in infants globally.

Nirsevimab is administered as a single injection of monoclonal antibodies, offering protection within a week of administration and lasting at least five months—enough to cover the entire RSV season in many countries. WHO guidelines recommend giving infants a dose of nirsevimab at birth or before discharge from a birthing facility.

Experts say the findings underscore the urgent need for preventive strategies to tackle RSV, particularly in infants during their most vulnerable months.