There is no traditional vaccine given directly to babies for RSV, but two highly effective options now exist to protect infants. One is a single-shot antibody injection given to the baby, and the other is a vaccine given to the mother during pregnancy that passes protection to the baby before birth. Both became available starting in 2023, and they represent a major shift in how RSV is prevented in young children.
Why Babies Don’t Get a Traditional RSV Vaccine
Infant immune systems are too immature to mount a strong response to a conventional vaccine against RSV. Instead, both available options work through passive immunity, meaning the baby receives ready-made protective antibodies rather than being prompted to build its own. This provides immediate protection but is temporary, lasting weeks to months rather than years. For RSV, that window of protection is exactly what’s needed, since the virus is most dangerous in the first six months of life.
The Antibody Shot Given to Babies
The primary option for most infants is nirsevimab (sold as Beyfortus), a lab-made antibody given as a single injection. It’s not technically a vaccine. It delivers one specific antibody that blocks RSV from infecting cells in the lungs and airways. A single dose provides protection through an entire RSV season, which typically runs from fall through spring.
The protection is substantial. In real-world effectiveness data published in Pediatrics, nirsevimab reduced RSV-related lower respiratory tract disease by 87% and cut RSV hospitalizations by 98%. Even against any lab-confirmed RSV infection, it was 71% effective. Side effects in clinical trials were uncommon: only about 1.2% of babies who received the shot had any adverse event within a year, and 97% of those were mild to moderate. The most frequently reported reactions were a mild rash (in less than 1% of recipients) and minor irritation at the injection site.
Nirsevimab is recommended for all infants younger than 8 months who are born during or entering their first RSV season, as long as their mother did not receive the RSV vaccine during pregnancy. It’s also recommended if the mother’s vaccination status is unknown or if the baby was born within 14 days of the mother getting vaccinated, since antibodies wouldn’t have had enough time to transfer. The dose is weight-based: babies under about 11 pounds get a smaller dose, while those 11 pounds and over get a larger one.
The Vaccine Given During Pregnancy
The second option is a vaccine called Abrysvo, given to the pregnant person rather than the baby. The CDC recommends it between 32 and 36 weeks of pregnancy. It works by stimulating the mother’s immune system to produce RSV antibodies, which then cross the placenta and are present in the baby at birth.
Protection is strongest in the first three months of life: the maternal vaccine reduced RSV hospitalization risk by 68% and healthcare visits for RSV by 57% during that window. It was especially effective at preventing severe outcomes like dangerously low oxygen levels, the need for a breathing machine, or ICU admission, cutting those risks by 82% in the first three months. By six months after birth, the protection fades somewhat but remains meaningful, with a 57% reduction in hospitalization and a 69% reduction in severe outcomes.
The key tradeoff is that the maternal vaccine provides less protection than the antibody shot given directly to the baby, but it eliminates the need for a separate injection after birth. Families typically choose one approach or the other. If the mother received the vaccine during pregnancy at the right time, the baby generally does not also need nirsevimab.
Protection for Older and Higher-Risk Infants
Some children between 8 and 19 months old qualify for nirsevimab heading into their second RSV season if they have certain health conditions that put them at higher risk for severe illness. These include chronic lung disease, significant congenital heart defects, conditions that weaken the immune system (such as chemotherapy), neuromuscular disorders that make it hard to cough and clear the airways, and congenital abnormalities of the lungs. The dose for this older age group is larger and given as two separate injections at the same visit.
Before nirsevimab became available, a different monthly antibody injection called palivizumab was the only option, and it was reserved exclusively for high-risk babies, particularly those born very prematurely or with chronic lung or heart conditions. Palivizumab required five monthly doses across the RSV season, making it far more burdensome. Nirsevimab has largely replaced it for most infants since it requires only one dose.
Cost and Access
Nirsevimab is covered by most insurance plans, and for uninsured or underinsured families, the Vaccines for Children (VFC) program provides it at no cost through enrolled healthcare providers. The CDC has specifically encouraged birthing hospitals to enroll in the VFC program so babies can receive the shot before they even go home, which is especially important for families who may not have a well-child visit scheduled within the first week of life. Hospitals and nurseries can register as specialty VFC providers to stock nirsevimab and hepatitis B vaccine specifically for newborns.
If your baby was born outside of RSV season and is approaching fall or winter without protection, a pediatrician can administer nirsevimab at a routine visit before the season picks up. Timing matters more than age: the goal is to have protection in place before RSV begins circulating in your community.