A little more protection for infants? Yes! The FDA recently approved a breakthrough in infant health: Enflonsia, a new, preventative antibody shot designed to shield babies under 1 year old from RSV. Known as Respiratory Syncytial Virus, RSV is the leading cause of infant hospitalizations in the U.S. The respiratory virus poses a serious threat to young children, but with Enflonsia, families have a powerful new tool for protection. Drugmaker Merck says it’s moving quickly to make the shot available ahead of the upcoming RSV season.
RSV Protection for Infants
RSV can start out looking like a common cold — but in infants, it can quickly turn serious. While mild cases can seem harmless, more severe infections can lead to alarming symptoms like wheezing, difficulty breathing, and even apnea. In some cases, RSV progresses to bronchiolitis or pneumonia, both of which can require hospitalization. While RSV poses a serious threat to infants and older adults, vaccine protection looks very different depending on age.
Currently, there are three approved RSV vaccines for adults. But for infants, the options are more limited, and there is still no RSV vaccine approved for direct use in babies.
Workarounds for Babies
However, there’s one workaround: Abrysvo, a maternal RSV vaccine can be given during pregnancy. It helps protect newborns by passing antibodies through the placenta, offering up to six months of protection after birth.
For babies already born, there’s a different tool: Nirsevimab (sold under the brand name Beyfortus), a monoclonal antibody shot. The CDC recommends it for infants younger than 8 months entering their first RSV season — especially if the mother didn’t get vaccinated during pregnancy.
While vaccines train the body to create its own immunity (active immunity), monoclonal antibodies deliver ready-made protection (passive immunity). The science behind each is different, but what matters is both can provide strong, timely defense against RSV. And most infants don’t need both.
Designed for All Infants
Enflonsia is the newest player in RSV protection for infants. It’s the first and only RSV preventative shot designed for single-dose use across all infants. This includes healthy, premature, full-term, or infants considered at-risk. It’s not a vaccine but a monoclonal antibody with the potential to prevent RSV in babies under one year of age.
According to Reuters, Enflonsia is expected to be available ahead of the upcoming RSV season — a much-needed backup after last year’s shortage of Beyfortus left many families scrambling.
