FDA Approves Preventative Therapy for Respiratory Syncytial Virus in Infants and Toddlers

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The new drug may help vulnerable children resist RSV in the coming fall and winter season.

On July 17, 2023, FDA approved nirsevimab-alip for newborns and infants born during or entering their first season of Respiratory Syncytial Virus (RSV), and children up to 24 months during their second RSV season who are vulnerable to severe RSV disease. Nirsevimab-alip—brand name Beyfortus—is a monoclonal antibody (mAB) that is administered as a single intramuscularly injection before or during the RSV season, according to FDA. One dose may prevent RSV during the entire season.

To support the safety and effectiveness of nirsevimab-alip, three clinical trials were conducted (Trials 03, 04, and 05). Efficacy was measured by the occurrence of RSV lower respiratory tract infection (MA RSV LRTI) during a period of 150 days after nirsevimab-alip injection. Trial 03—a randomized, double-blind, and placebo-controlled multicenter clinical trial—included 1453 preterm infants born during or entering their first RSV season. Nirsevimab-alip reduced the risk of MA RSV LRTI by around 70% relative to placebo. Trial 04 analyzed 1490 term and late preterm infants, and nirsevimab-alip reduced the risk of MA RSV LRTI by around 75% relative to placebo.

FDA reported that Trial 5—a randomized, double-blind, active (palivizumab)-controlled, multicenter trial—supported the use of nirsevimab-alip “in children up to 24 months of age who remain vulnerable to severe RSV disease through their second RSV season. The trial enrolled 925 preterm infants and infants with chronic lung disease of prematurity or congenital heart disease.”

Nirsevimab-alip’s potential side effects include rash and injection site reactions. Infants and children with a history of serious reactions to its active ingredients or excipients should not take nirsevimab-alip. FDA cautioned that nirsevimab-alip “comes with warnings and precautions about serious hypersensitivity reactions, including anaphylaxis, which have been observed with other human IgG1 monoclonal antibodies.” Use of nirsevimab-alip in infants and children with clinically significant bleeding disorders should be done with caution.


“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, M.D., M.P.H., director of the Office of Infectious Diseases in FDA’s Center for Drug Evaluation and Research, in an FDA press release. “Today’s approval addresses the great need for products to help reduce the impact of RSV disease on children, families and the health care system.”

RSV is a virus with the potential to cause acute respiratory infection in all age groups. Most infants and young children experience mild cold-like symptoms, but some infants (particularly if it is their first infection) develop lower respiratory tract diseases such as pneumonia and bronchiolitis. These diseases cause swelling on small airway passages in the lungs and often lead to trips to the physician or ER. RSV poses the highest risk to premature infants, and those with chronic lung disease of prematurity or significant congenital heart disease. RSV circulation is seasonal in most of the United States, starting in the fall and peaking in the winter, and is transmitted through close contact with someone who is infected, according to FDA.

Sources: FDA