New RSV protection for infantswhat changed in 2025

Why does RSV get this much attention for babies?

Respiratory syncytial virus (RSV) is a common respiratory virus that's usually mild in older children and adults but can cause serious lower respiratory tract infections, like bronchiolitis or pneumonia, in very young infants. It's a leading cause of hospitalization in babies under a year old. Until recently, there was no way to directly protect infants beyond general hygiene and, for high-risk babies, a monthly antibody injection through the whole season. That changed with a maternal vaccine and then long-acting antibody shots that need only a single dose.

What are the three prevention options now?

• Maternal RSV vaccine (Abrysvo). Given to the pregnant parent, typically between weeks 32 and 36 of pregnancy, during RSV season. The vaccine prompts the mother's body to make antibodies that cross the placenta and protect the baby from birth.
• Nirsevimab (Beyfortus). A single long-acting monoclonal antibody injection given directly to the infant, ideally at birth or shortly after, that provides several months of passive protection through one RSV season.
• Clesrovimab (Enflonsia). A newer long-acting monoclonal antibody for infants, recommended by ACIP in June 2025 as a second antibody option alongside nirsevimab.

All three work by giving the baby ready-made antibodies rather than asking their immune system to build a response from scratch, which is why they can protect newborns whose own immune systems are still immature.

Does my baby need the vaccine, the antibody, or both?

Current CDC guidance is clear that most infants will not need both maternal vaccination and an infant antibody. An infant antibody (nirsevimab or clesrovimab) is generally recommended for infants younger than 8 months who are born during or entering their first RSV season, when: the mother did not receive the RSV vaccine during pregnancy; the mother's vaccination status is unknown; or the baby was born within 14 days of the mother's vaccination, which isn't enough time for protective antibodies to transfer fully. If the mother was vaccinated in time, the baby typically doesn't need the extra antibody shot for that first season.

This is a conversation to have with your OB before birth and with your pediatrician at or after delivery, since eligibility depends on timing and season, not just a blanket rule.

How well do these actually work?

Based on published data, nirsevimab has shown roughly 70-80% effectiveness against RSV-associated hospitalization in real-world use. Clesrovimab, in the trial supporting its 2025 recommendation, showed about 60% efficacy against medically attended RSV lower respiratory infections and around 91% efficacy against RSV-related hospitalization, with a safety profile similar to placebo. ACIP has not stated a preference between nirsevimab and clesrovimab — the choice generally comes down to what's available, timing, and your pediatrician's practice.

When does this matter during the year?

RSV circulates seasonally in most of the U.S., roughly October through March, similar to flu season. Infant antibody doses are typically given during this window, ideally during the birth hospitalization for babies born in season, or as a catch-up dose before season starts for babies born earlier in the year. If you're pregnant and due around RSV season, ask about vaccine timing at a prenatal visit rather than after the fact, since the 32-36 week window is specific.

What about symptoms and when to seek care?

Prevention lowers risk but doesn't eliminate it, so it still helps to know the warning signs of a serious respiratory infection in a young infant: fast or labored breathing, flaring nostrils, ribs pulling in with each breath, a bluish tint to lips or face, poor feeding, unusual lethargy, or a high fever in a very young baby. These need urgent medical attention regardless of whether your baby received an RSV vaccine or antibody, since protection is strong but not absolute.

How can you keep track of what your baby's had?

Between vaccines, antibody doses, and well-child visits, it's easy to lose track of exactly what was given and when, especially with a newborn and very little sleep. Mommy Refuel, a free iPhone app for the whole parenting journey, includes tools like doctor visit summaries to help you keep notes and questions organized between appointments. It's not a medical record system and doesn't replace your pediatrician's own documentation, but it can make follow-up conversations easier.