RSV causes mild cold-like symptoms in most people, but it’s the leading cause for hospitalization among infants in the U.S. In babies, the virus can cause mild illness or it can cause dangerous inflammation in a child’s tiny airways.

“There's really no way to predict how your child would do even if they're completely healthy,” said Priya Soni, MD, a pediatric infectious disease specialist at Cedars-Sinai Guerin Children’s. “If they do end up having a horrible course with RSV, they will likely need to be hospitalized for oxygen support, fluids and other supportive measures.”

Most children in the U.S. will be infected with RSV within the first year of their life, and almost all infants will have been exposed to the virus by the time they're 2 years old.

But parents of infants have a new way to protect their children. The U.S. Food and Drug Administration (FDA) recently approved an immunization—a monoclonal antibody treatment called nirsevimab-alip (Beyfortus)—that can be given as a single-dose shot to newborns and infants during their first RSV season. Children up to 19 months old who remain vulnerable to severe disease in their second RSV season also can get the shot.

Soni said she “100%” recommends the immunization because of strong clinical trials that yielded positive results.

The FDA also recently approved a Pfizer RSV vaccine for women who are 32-36 weeks pregnant to protect their infants at birth. The same vaccine also was approved for adults 60 and older, as was another vaccine from pharmaceutical company GSK.

For older adults, the Centers for Disease Control and Prevention (CDC) recommended these new vaccines only for those who are at highest risk of severe RSV, such as patients with asthma, diabetes or heart failure. Although both vaccines are considered safe, a very small number of cases of Guillain-Barre syndrome—a condition in which a person’s immune system attacks their peripheral nerves—were reported after vaccination.

More data is needed to determine whether these episodes may have been unrelated to the vaccine, according to the CDC. But the significant risk RSV poses to some older adults could outweigh the very low risk of developing potential side effects.

Sonja Rosen, MD, section chief of Geriatric Medicine at Cedars-Sinai, said that for now,  she recommends the RSV vaccine for older patients with lung disease, or for those who are otherwise immunosuppressed and therefore at higher risk for severe illness. “Patients should speak with their physician and make an informed decision about whether this shot is right for them,” Rosen said.