The FDA has approved a new preventive shot designed to protect infants from respiratory syncytial virus (RSV), offering a streamlined and effective option for parents and caregivers. The shot, called Enflonsia, contains the antibody clesrovimab and is intended to protect babies during their first RSV season, which typically spans from fall through spring.
RSV is a common respiratory virus that often causes cold-like symptoms but can lead to severe illness in infants, especially those under six months old. It spreads easily through coughing, sneezing, direct contact, or touching contaminated surfaces. In vulnerable populations like infants and older adults, RSV can cause bronchiolitis and pneumonia, which may require hospitalization. It is one of the leading causes of infant hospitalizations in the United States, making prevention a high priority.
Enflonsia offers a new approach by using a single, fixed 105-mg dose for all babies, regardless of weight. This simplifies administration and ensures consistent protection across the infant population. The shot provides protection for up to five months, aligning with the typical duration of RSV season. It is administered as a single injection in the thigh.
Clinical trials demonstrated that Enflonsia significantly reduced the risk of severe RSV-related lung infections and hospitalizations. In one study, a single dose lowered the rate of serious lung infections by 60% and hospitalizations by 84% over a five-month period compared to a placebo. A second trial confirmed that the shot was as effective and safe as palivizumab, an existing RSV medicine used for high-risk infants, such as those born prematurely or with underlying lung or heart conditions.
Importantly, Enflonsia was shown to be safe when given alone or alongside routine childhood vaccines. The most commonly reported side effects included mild redness or swelling at the injection site and occasional mild skin rashes. After receiving the injection, babies will be monitored for any signs of a serious allergic reaction, although such events are expected to be rare.
The shot is recommended for babies born during RSV season to be given at birth. Infants born outside of RSV season should receive the injection just before the season begins to ensure maximum protection.
With its convenient dosing and robust clinical trial results, Enflonsia marks a significant advancement in preventing RSV-related complications in infants. As the virus continues to pose a seasonal threat to young children, this new option offers a practical and reliable way to reduce severe outcomes and hospitalizations during their most vulnerable months.
