Beyfortus is a brand-name injection prescribed to help prevent severe illness caused by respiratory syncytial virus (RSV) infection in certain children. Beyfortus contains the active drug nirsevimab-alip and belongs to the monoclonal antibody drug class.
RSV is a viral respiratory infection that commonly affects young children. It usually causes mild symptoms similar to the common cold. But in some children, RSV infection can cause severe illness that needs treatment in a hospital.
Beyfortus is FDA-approved to help prevent severe illness caused by RSV infection in:
- babies younger than 1 year born during or entering their first RSV season (fall to spring)
- children younger than age 2 years who are still at high risk of severe RSV-related illness during their second RSV season
You’ll find key information about Beyfortus below.
- Drug class: monoclonal antibody
- Drug form: injection
- Generic available? no
- Prescription required? yes
- Controlled substance? no
- Year of FDA approval: 2023
Traditional drugs are made using chemicals. But biologic drugs are made using living cells. It’s possible to make exact copies of brand-name chemical drugs. These are called generics. But it’s not possible to make exact copies of brand-name biologic drugs. Manufacturers can make biosimilars instead.
Generics and biosimilars are considered to be as safe and effective as the original brand-name drug.
They tend to cost less than brand-name drugs.
The Food and Drug Administration (FDA) approves prescription drugs such as Beyfortus to treat certain conditions.
Beyfortus for respiratory syncytial virus
Respiratory syncytial virus (RSV) is a highly contagious respiratory virus that commonly affects young children. It usually causes mild symptoms, similar to the common cold. But in some children, RSV infection can cause severe illness that needs treatment in a hospital.
Beyfortus is FDA-approved to help prevent severe illness caused by RSV infection in:
- babies younger than 1 year born during or entering the RSV season (fall to spring)
- children younger than age 2 years who are still at high risk* of severe RSV-related illness during their second RSV season
* Children still at high risk of severe RSV-related illness after their first birthday include those with weakened immune systems. It also includes those with long-term heart or lung disease and neuromuscular disorders such as muscular dystrophy.
As with all medications, the cost of Beyfortus can vary. The actual price you’ll pay depends on your insurance plan, your location, and the pharmacy you use.
Financial and insurance assistance: If you need financial support to pay for Beyfortus or help to understand your insurance coverage, help is available.
To learn more about saving money on prescriptions, check out this article.
Biosimilar form: Beyfortus is a biologic drug that’s available only as a brand-name medication. It’s not currently available in biosimilar form.
Traditional drugs are made using chemicals. But biologic drugs are made using living cells. It’s not possible to make exact copies of brand-name biologic drugs. Manufacturers can make biosimilars instead.
Biosimilars tend to cost less than brand-name drugs.
The Beyfortus dosage your child’s doctor prescribes will depend on several factors. These include your child’s age and body weight.
The following information describes dosages that are commonly used or recommended. However, your child’s doctor will determine the best dosage to fit your child’s needs.
Drug forms and strengths
Beyfortus comes as a liquid solution inside single-dose prefilled syringes. It’s available in two strengths:
- 50 milligrams (mg) in 0.5 milliliters (mL)
- 100 mg/1 mL
Your child’s doctor will administer Beyfortus by intramuscular injection (injection into a muscle). They’ll usually administer the injection into your child’s thigh.
Dosage for respiratory syncytial virus
The recommended dosages for preventing severe illness caused by respiratory syncytial virus (RSV) in children are described below.
For babies younger than 1 year born during or entering their first RSV season (fall to spring):
- babies weighing less than 5 kilograms (kg)*: one injection of 50 mg
- babies weighing 5 kg or more: one injection of 100 mg
For children younger than age 2 years who are still at high risk of severe RSV-related illness during their second RSV season: 200 mg, given as two injections of 100 mg.
Each dose of Beyfortus helps prevent severe RSV-related illness for about 5 months, which is the usual length of the RSV season. The protection Beyfortus gives the child wears off over time.
Children who have had certain types of heart surgery may have a particularly high risk of severe RSV-related illness. It’s recommended that these children are given an extra dose of Beyfortus as soon as they’re stable after their surgery. If your child is due to have heart surgery, talk with their doctor about whether they’ll need an extra dose of Beyfortus and what dose will be given.
* 1 kg is about 2.2 pounds (lb).
Beyfortus can cause mild or serious side effects. The following lists contain some of the key side effects that may occur after receiving Beyfortus. These lists do not include all possible side effects.
For more information about the possible side effects of Beyfortus, talk with your doctor or pharmacist. They can give you tips on how to manage any side effects that may be concerning or bothersome.
Note: The Food and Drug Administration (FDA) tracks side effects of drugs it has approved. If you’d like to notify the FDA about a side effect your child has had with Beyfortus, you can do so through MedWatch.
Mild side effects
Below is a partial list of mild side effects of Beyfortus. To learn about other mild side effects, talk with your doctor or pharmacist, or view Beyfortus’s prescribing information.
Mild side effects of Beyfortus can include:
- skin rash
- injection site reactions, such as pain, swelling, redness, or discoloration at the injection site
- mild allergic reaction*
Most of these side effects may go away within a few days to a couple of weeks. However, if they become more severe or don’t go away, talk with your doctor or pharmacist.
* For more information about allergic reaction and Beyfortus, see “Allergic reaction” below.
Serious side effects
Serious side effects from Beyfortus aren’t common, but they can occur. Call your doctor right away if your child has serious side effects. Call 911 or your local emergency number if your child’s symptoms seem life threatening or if you think they’re having a medical emergency.
A serious side effect can include severe allergic reaction. For details about allergic reaction and Beyfortus, see “Allergic reaction” below.
Symptoms of a mild allergic reaction can include:
A more severe allergic reaction is rare but possible. Symptoms of a severe allergic reaction can include:
- swelling under your skin, typically in your eyelids, lips, hands, or feet
- swelling of your tongue, mouth, or throat
- trouble breathing
Call your doctor right away if your child has an allergic reaction to Beyfortus, as the reaction could become severe. Call 911 or your local emergency number if your child’s symptoms seem life threatening or if you think your child is having a medical emergency.
However, this doesn’t mean that interactions won’t be recognized in the future. For example, new drugs could be approved that interact with Beyfortus.
Before your child receives Beyfortus, talk with your child’s doctor and pharmacist. Tell them about any prescription, over-the-counter, or other drugs your child takes. Also, tell them about any vitamins, herbs, and supplements your child takes. Sharing this information can help you avoid potential interactions.
If you have questions about drug interactions that may affect your child, talk with your child’s doctor or pharmacist.
Other drugs are available that can help prevent severe illness caused by respiratory syncytial virus (RSV) infection. Some may be a better fit for your child than others. If you’re interested in finding an alternative to Beyfortus, talk with your doctor. They can tell you about other medications that may work well for your child.
Palivizumab (Synagis) is a similar drug to Beyfortus. Palivizumab is the active drug in brand-name Synagis. The active drug in brand-name Beyfortus is nirsevimab-alip.
Here are answers to some frequently asked questions about Beyfortus.
How does Beyfortus work?
Beyfortus is prescribed to help prevent severe illness caused by respiratory syncytial virus (RSV) infection in young children. It works by helping your child’s immune system attack the virus. (Your immune system is your body’s defense system.) Young children’s immune systems are not fully developed, so they have a higher risk of severe illness with this common virus.
Beyfortus is a type of drug called a monoclonal antibody. Antibodies are proteins that help your immune system recognize and attack certain other proteins, such as those found on the surface of viruses. They help protect you from illness. A monoclonal antibody is a lab-made antibody that helps your immune system find and attack a particular protein.
Beyfortus helps your child’s immune system find and attack a protein found on the respiratory syncytial virus. If your child becomes infected with RSV, Beyfortus helps their immune system to kill the virus. This helps prevent RSV causing severe illness.
If you have questions about how Beyfortus works, talk with your child’s doctor or pharmacist.
Is Beyfortus effective?
Yes, Beyfortus has been found effective for helping prevent severe illness caused by RSV infection in young children.
Clinical trials of Beyfortus showed it was safe and effective for all infants under age 1 year entering their first RSV season. The drug is also effective for children younger than age 2 years who are at high risk of severe disease entering their second RSV season. The FDA approved Beyfortus based on these age ranges.
To find out how the drug performed in clinical trials, see the prescribing information for Beyfortus. You can also talk with your child’s doctor or pharmacist.
Can Beyfortus cause long-term side effects?
At this time, Beyfortus is not known to cause long-term side effects. No long-term side effects were reported in clinical trials of the drug.
If you’re concerned about the risk of side effects with Beyfortus, talk with your child’s doctor.
This drug comes with some precautions.
Before your child receives Beyfortus, discuss their health history with your child’s doctor. Beyfortus may not be right for your child if they have certain medical conditions or other factors affecting their health. Be sure to talk with your child’s doctor if any of the following apply to your child:
- blood clotting disorders, such as factor V Leiden
- thrombocytopenia (low platelet count)
- bruising or bleeding problems
- previous allergic reaction to this or a similar drug
Note: For more information about the potential negative effects of Beyfortus, see the “Beyfortus side effects” section above.
Disclaimer: Medical News Today has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.