Join the more than 11 million* babies who have already been immunized with Beyfortus
*This number is based on sales data (through Oct 2025).
What is RSV?
RSV, or respiratory syncytial virus, is a common virus that spreads quickly and unpredictably. It spreads most easily from fall to spring, usually peaking in the winter (Dec-Feb). As a parent, it’s important to learn about RSV and how Beyfortus—a single-dose RSV antibody protection for babies—can help protect your baby from serious RSV lung infection.
RSV is unpredictable—while most cases are mild, it’s hard to know which babies will get it or how severe it may become.
RSV is a leading cause of hospitalization in babies under 1.
More than half of all babies will get RSV by age 1.
Get to know Beyfortus
Beyfortus is a preventive antibody designed to help protect babies from serious RSV lung infection. It's not a vaccine. Instead, Beyfortus works by providing the cells that a baby's developing immune system lacks to help them fight RSV right away.
Beyfortus is the #1 prescribed RSV protection for babies.* It's used for babies entering their first RSV season and may be given in the hospital at birth or during any visit with their doctor within their first year. Now's a good time to explore how Beyfortus can help protect your baby this RSV season.
*IQVIA data through March 2026.
How long does Beyfortus last?
Beyfortus can help give your baby long-lasting protection throughout their first RSV season, which is usually around five months.
Is Beyfortus right for my baby?
Beyfortus is a prescription medicine used to help prevent a serious lung disease caused by Respiratory Syncytial Virus (RSV) in:
- Newborns and babies under 1 year of age born during or entering their first RSV season.
- Children up to 24 months of age who remain at risk of severe RSV disease through their second RSV season.
Support & resources
Ready to talk to your baby’s doctor? We can help.
Starting the conversation about RSV protection can be overwhelming, but we can help. Bring our doctor discussion guides to your next visit to help you lead the conversation.
Parent-to-be guide PDF
New parent guide PDF
Help and guidance from day one
Whether you’re learning about RSV for the first time or getting ready for a visit with your baby's doctor, we’re here to help. On our Resources for Parents page, you can sign up for personalized updates and download helpful resources—all in one place.
Affordable RSV protection starts here
Beyfortus is available for most babies, and may be available at no cost to you. Most private insurance plans cover Beyfortus, and it’s also available through the Vaccines for Children (VFC) program. Our Cost & Coverage page can help you understand your options, and you can ask your child's doctor about them today.
Your child should not take Beyfortus if your child has a history of serious allergic reactions to nirsevimab-alip or any of the ingredients in Beyfortus.
Before your child receives Beyfortus, tell your healthcare provider about all of your child’s medical conditions, including if your child:
- has ever had a reaction to Beyfortus.
- has bleeding or bruising problems. If your child has a problem with bleeding or bruises easily, an injection could cause a problem.
Tell your healthcare provider about all the medicines your child takes, including prescription and over-the-counter medicines, vitamins, and herbal supplements. Your infant should not receive a medicine called palivizumab if they have already received Beyfortus in the same RSV season.
Serious allergic reactions have happened with Beyfortus. Get medical help right away if your child has any of the following signs or symptoms of a serious allergic reaction:
- swelling of the face, mouth, or tongue
- difficulty swallowing or breathing
- unresponsiveness
- bluish color of skin, lips, or under fingernails
- muscle weakness
- severe rash, hives, or itching
The most common side effects of Beyfortus include rash and pain, swelling, or hardness at the site of your child’s injection. These are not all the possible side effects of Beyfortus. Call your healthcare provider if you have questions about side effects.
Please see full Prescribing Information, including Patient Information, for more details.
Click here to learn more about Sanofi’s commitment to fighting counterfeit drugs.
Beyfortus is a prescription medicine used to help prevent a serious lung disease caused by Respiratory Syncytial Virus (RSV) in:
- Newborns and babies under 1 year of age born during or entering their first RSV season.
- Children up to 24 months of age who remain at risk of severe RSV disease through their second RSV season.