Beyfortus (cvx 307) is a man-made antibody that helps protect the body against respiratory syncytial virus (RSV) infection for up to 5 months.

Beyfortus (cvx 307) is used to prevent lung disease caused by respiratory syncytial virus in newborn baby and children up to 24 months old.

Beyfortus (cvx 307) may also be used for purposes not listed in this medication guide.

Beyfortus (cvx 307) should not be given to a child who has had a severe allergic reaction to it.

Your child should not receive a medicine called palivizumab if the child already received Beyfortus (cvx 307) in the same respiratory syncytial virus (RSV) season.

Beyfortus (cvx 307) is given once as an injection (shot) into the leg muscle. A healthcare provider will give this injection.

If your child remains at increased risk for getting RSV infection or has heart surgery, your child may receive another dose of this medicine.

Your child should not receive Beyfortus (cvx 307) if the child has ever had a life-threatening allergic reaction to any component of Beyfortus (cvx 307) or to antibodies called immunoglobulins.

Your child should not receive a medicine called palivizumab if the child already received Beyfortus (cvx 307) in the same RSV season.

Tell your child's doctor if the child has bleeding or bruising problems.

Beyfortus (cvx 307) is used as a single dose and does not have a daily dosing schedule.

An overdose of nirsevimab is unlikely to occur.

Follow the doctor's instructions about any restrictions on food, beverages, or activity.

Get emergency medical help if you have signs of an allergic reaction: hives, difficult breathing, swelling of the face, lips, tongue, or throat.

Call the doctor at once if your child has:

• muscle weakness;

• trouble swallowing;

• blue lips or fingernails; or

• bluish color of skin.

Common side effects of Beyfortus (cvx 307) may include:

• hard painful lump (induration) around where the medicine was injected; or

• rash, or swelling where the injection was given.

This is not a complete list of side effects and others may occur. Call your child's doctor for medical advice about side effects. You may report side effects to FDA at 1 800 FDA 1088.

Other drugs may affect Beyfortus (cvx 307), including prescription and over-the-counter medicines, vitamins, and herbal products. Tell the doctor about all other medicines your child uses.