Beyfortus

Pronunciation: Bay-for-Tus
Generic name: nirsevimab-alip
Dosage form: intramuscular injection
Drug class: Antiviral monoclonal antibodies

Medically reviewed by Carmen Pope, BPharm. Last updated on Oct 17, 2024.

What is Beyfortus?

Beyfortus is used to protect babies under 1 year of age from serious RSV lung infections. Beyfortus may also be given to children up to 2 years old (24 months) who remain at risk of severe RSV disease through their second RSV season.

• Beyfortus provides immediate and short-term protection against RSV for around 5 months.
• RSV is an abbreviation for respiratory syncytial virus. See here for symptoms of RSV.
• Beyfortus is technically not a vaccine because it does not teach the immune system to create its own antibodies as a vaccine does. Instead, it already contains the antibodies, which allows it to provide fast-acting protection against RSV. 

How does Beyfortus work?

Beyfortus's mechanism of action involves providing passive protection against RSV to infants when they are at their most vulnerable (their first year of life). Beyfortus contains a long-acting monoclonal antibody, called nirsevimab-alip, that targets the RSV F protein, stopping the virus from entering cells and multiplying. Beyfortus is administered to infants before and during the RSV season to reduce the risk of severe lower respiratory tract infections caused by RSV.

When was Beyfortus approved?

Beyfortus gained FDA approval on July 17, 2023. There is no Beyfortus generic.

Beyfortus cost

Beyfortus is included in the approved immunization schedule and may be available at no cost for parents through private health insurance companies and the Vaccines for Children (VFC) program. See here for more details.

Beyfortus side effects

The most common side effects of the Beyfortus vaccine are:

• a rash
• pain, swelling, redness, or a hard area at the site where your child got their injection. 

Serious side effects and warnings

Beyfortus may cause serious hypersensitivity reactions, including anaphylaxis. Your child should not receive Beyfortus if they have had serious allergic reactions in the past to nirsevimab-alip, Beyfortus, or any inactive
ingredients in the Beyfortus injection. 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 or loss of muscle tone (goes floppy)
• bluish color of skin, lips, or under the fingernails
• muscle weakness
• severe rash, hives (urticaria), or itching.

Beyfortus should be used with caution in infants and children with bleeding or clotting disorders, or in those taking anticoagulants.

Beyfortus may not protect all children.

It is not known if Beyfortus is safe and effective in children older than 24 months of age.

These are not all of the possible side effects of Beyfortus. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Related/similar drugs

Before taking

Your child should not receive the Beyfortus vaccine if they have had serious allergic reactions in the past to nirsevimab-alip, Beyfortus, or any inactive ingredients in the Beyfortus injection.

Before your child receives Beyfortus, tell your healthcare provider about all of your child's medical conditions, including if your child:

• has ever reacted Beyfortus or nirsevimab-alip
• has bleeding or bruising problems. If your child has a problem with bleeding or bruises easily, an injection could cause a problem.

Beyfortus should not be used in older children (more than 2 years [24 months] old).

How is Beyfortus given?

Beyfortus is given by a healthcare provider as an injection into the upper thigh.

• Usually, only 1 dose is needed.
• A second dose may be given if your child remains at increased risk for RSV the following year.

Your child should be given Beyfortus before the start, at the start, or during the RSV season. 

• RSV season is the time of year when RSV infections are most common, usually occurring late fall (November) through spring (April) with a peak in January and February.
• Your healthcare provider can tell you when the RSV season starts in your area.
• Your child may still get RSV disease after receiving Beyfortus. Talk to your child’s healthcare provider about what symptoms to look for.

If your child has heart surgery, your child’s healthcare provider may need to give your child an additional Beyfortus injection soon after surgery.

Beyfortus can be administered at the same time as childhood vaccines, at a different injection site. Do not mix Beyfortus with any vaccines or medications in the same syringe or vial.

Beyfortus dosing

Beyfortus is available as a single-dose pre-filled syringe in 2 strengths:

• Beyfortus 50 mg/0.5 ml for infants less than 5 kg (11 lb) in body weight
• Beyfortus 100 mg/ml for infants more than or equal to 5 kg (11 lb) in body weight.

The dosage of Beyfortus depends on your child's weight and if it is their first or second RSV season.

Beyfortus dosage for infants under 1 year born during or entering their first RSV season:

• Less than 5 kg: Beyfortus 50 mg
• More than or equal to 5 kg: Beyfortus 100 mg

Beyfortus dosage for children who remain vulnerable through their second RSV season:

• Beyfortus 200 mg (2 x 100 mg injections), regardless of weight.

Is Beyfortus a vaccine?

Technically, Beyfortus is not a vaccine, because it provides infants with the antibodies needed to protect them against RSV, unlike vaccines that teach your immune system to make its own antibodies. This is called passive protection. Beyfortus protects your baby immediately from getting sick with RSV, and the protection lasts for about 5 months.

What other drugs will affect Beyfortus?

Other drugs may interact with Beyfortus, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all the current medicines your baby takes. Especially tell your healthcare provider if your baby:

• has received palivizumab (another monoclonal antibody for RSV) recently
• receives anticoagulants (such as heparin or warfarin).

This list is not complete. See the Beyfortus prescribing information for a full list of interactions.

Beyfortus ingredients

Active ingredients: nirsevimab-alip.
Inactive ingredients: L-histidine, L-histidine hydrochloride, L-arginine hydrochloride, sucrose, polysorbate 80, water for injections.

Available as:

• Beyfortus 50 mg/0.5 mL in a single-dose pre-filled syringe
• Beyfortus 100 mg/1 mL in a single-dose pre-filled syringe.

Who makes Beyfortus?

Astra Zeneca AB makes Beyfortus and Sanofi Pasteur, Inc. distributes it.

Beyfortus Biosimilars

Biosimilar and interchangeable products are biological products that are highly similar to and have no clinically meaningful differences from the reference product.

Reference products

These are biological products that have already been approved by the FDA, against which biosimilar products are compared. There is 1 for Beyfortus.

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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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