Beyfortus

Pronunciation: BAY-for-TUS
Generic name: nirsevimab-alip
Dosage form: intramuscular injection
Drug class: Other immunostimulants

Medically reviewed by Carmen Pope, BPharm. Last updated on Jul 15, 2024.

What is Beyfortus?

Beyfortus (nirsevimab-alip) is an injectable preventive antibody that may be used to protect newborns and babies under 1 year of age from serious lung infections caused by respiratory syncytial virus (RSV). It may also be given to children up to 24 months of age who remain at risk of severe RSV disease through their second RSV season. Beyfortus provides passive immunization and immediate and short-term protection against RSV that generally lasts around 5 months. 

Beyfortus contains nirsevimab-alip, a long-acting monoclonal antibody that provides babies with protection against RSV. Antibodies are made naturally by our immune system to fight pathogens and allergens but a baby's immune system is often not strong enough to make enough antibodies to fight RSV. Our immune system does not "learn" anything from antibodies, such as Beyfortus, instead, they protect against RSV during the time in a baby's life when they are most vulnerable.

Beyfortus was FDA-approved on July 17, 2023. 

Beyfortus side effects

The most common side effects of Beyfortus include:

• a rash
• pain, swelling, or hardness at the site of your child’s 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

Arexvy, Abrysvo, ribavirin, nirsevimab, palivizumab, mRESVIA, rsv vaccine pref3, recombinant

Before taking

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.

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 is not for use in children older than 2 years (24 months).

How is Beyfortus administered?

Beyfortus is given as an injection, usually into the thigh (leg muscle), by a healthcare provider.

• Usually, one dose is given.
• If your child remains at increased risk for RSV, they may receive a second dose in the second RSV season.

Your child should receive Beyfortus before 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 dosage

The dosage of Beyfortus depends on your child's weight and their exposure to RSV. 

Neonates and infants born during or entering their first RSV season:

• 50 mg if less than 5 kg (11 lb) in body weight
• 100 mg if greater than or equal to 5 kg (11 lb) in body weight.

Children who remain vulnerable through their second RSV season:

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

Beyfortus availability

Beyfortus is available through a hospital or your pediatrician. Contact your local health department for guidance.

Beyfortus is also available through the Vaccines for Children (VFC) Program. Children under 24 months who meet at least one of the following requirements may be eligible for no-cost vaccines:

• American Indian or Alaska Native
• Medicaid-eligible
• Uninsured
• Underinsured.

In 2023, there was a shortage of Beyfortus due to demand exceeding supply.

Is Beyfortus a vaccine?

Technically Beyfortus is not a vaccine, it provides infants with a quick defense against RSV. Unlike vaccines that train your body to fight germs, Beyfortus gives babies direct protection from RSV. It works right away to shield them from getting sick.

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:

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

Beyfortus is produced by recombinant DNA technology and is a human immunoglobulin G1 kappa (IgG1κ) monoclonal antibody. Triple amino acid substitution increases the length of time it stays effective.

Who makes Beyfortus?

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

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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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