The US Food and Drug Administration (FDA) on July 18 approved a drug to prevent Respiratory Syncytial Virus (RSV) in children aged up to 24 months who remain vulnerable to severe disease.

Developed by AstraZeneca and Sanofi, the drug Nirsevimab, sold under the brand name Beyfortus, is a monoclonal antibody that can prevent RSV. 

Nirsevimab is administered as a single injection either before or during an infant's first RSV season. Toddlers up to two years old who remain vulnerable can also receive the shot during their second RSV season.

"RSV can cause serious disease in infants and some children and results in a large number of emergency department and physician office visits each year," said John Farley, Director of the Office of Infectious Diseases in the FDA's Centre for Drug Evaluation and Research, in a statement.  

"Today's approval addresses the great need for products to help reduce the impact of RSV disease on children, families, and the healthcare system," he added. 

RSV is a virus that causes acute respiratory infection in individuals of all age groups.

While most infants and young children experience mild and cold-like symptoms, some infants, especially with their first infection, develop lower respiratory tract diseases such as pneumonia and bronchiolitis (swelling of the small airway passages in the lungs), which often leads to an emergency department or physician office visit. 

Premature infants, and those with chronic lung disease of prematurity or significant congenital heart disease, are at the highest risk for severe RSV disease. Nearly one to three percent of children aged under 12 months in the US are hospitalised each year due to RSV, according to the American Academy of Paediatrics. 

The FDA approval comes ahead of RSV season later this year. Recommendations on how the shot should be administered by doctors will be taken by the US Centers for Disease Control and Prevention's panel of independent experts in August.

At present, Palivizumab, sold under the brand name Synagis, is available to prevent RSV. But it is given mainly to infants who are preterm or who have lung and congenital heart conditions that put them at high risk of severe disease. 

Palivizumab is administered monthly throughout the RSV season.