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Overview: Enflonsia is a shot that is given to newborns and babies who are born during or entering their first respiratory syncytial virus (RSV) season. Enflonsia helps protect them for several months from lung disease like pneumonia or bronchiolitis caused by RSV. Your child may have redness or swelling where the shot is given. Get help right away if your child has any symptoms of a serious allergic reaction, such as trouble breathing or swelling of the face, mouth, or tongue.

Uses

What is Enflonsia used for?

Enflonsia (clesrovimab-cfor) is commonly used to help prevent lower respiratory tract disease caused by respiratory syncytial virus (RSV) in newborns and babies who are born during or entering their first RSV season.

Learn more about how Enflonsia can help prevent RSV.

How does Enflonsia work (mechanism of action)?

Enflonsia is an injection that delivers a type of protein (antibody) that protects against respiratory syncytial virus (RSV). This antibody helps block the virus from entering cells, which may help prevent severe lung problems caused by RSV. This is called passive immunization, which leads to passive immunity. Enflonsia offers protection throughout the RSV season (at least five months).

How is Enflonsia supplied (dosage forms)?

Enflonsia is available in an injectable form that is given by a health care provider. 

How should I store Enflonsia?

Enflonsia is usually given by a health care professional in a hospital, clinic, or pediatrician’s office. You will not store it at home.

Side Effects

What are the most common side effects of Enflonsia?

The most common side effects of Enflonsia are listed below. Tell your health care provider if your child has any of these side effects that bother you or them.

  • Redness or swelling near the injection site
  • Rash

There may be other side effects of Enflonsia that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of Enflonsia?

While less common, the most serious side effects of Enflonsia are described below, along with what to do if they happen.

Severe Allergic Reactions. Enflonsia may cause allergic reactions, which can be serious. Get help right away if your child has any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Muscle weakness
  • Skin, lips, or area under the fingernails is bluish in color
  • Not responding

Warnings & Precautions

Who should not use Enflonsia?

Allergies to Ingredients. People who are allergic to any of the following should not receive Enflonsia.

  • Clesrovimab-cfor
  • Enflonsia
  • Any of the ingredients in the specific product dispensed

Your child’s health care provider can tell you all of the ingredients in Enflonsia.

What should I know about Enflonsia before using it?

Enflonsia is a shot that is given by a health care provider. It is injected into a muscle. 

If your child needs vaccines, they may be given on the same day as Enflonsia. 

Your child should receive Enflonsia before or during respiratory syncytial virus (RSV) season, which is usually fall through spring. Your child’s health care provider can tell you when RSV season starts in your area, and when your child should receive Enflonsia.

Your child could still get RSV-related lung problems, even after receiving Enflonsia. Ask a health care provider about what symptoms to look for.

Tell your child's health care provider If you got a vaccine during pregnancy or your baby has already received a medicine to help prevent RSV. Many options exist to help prevent RSV in a baby.

Enflonsia may affect the results of some RSV tests. If a rapid RSV test comes back negative, another type of test (PCR) may be necessary to determine if your child has an RSV infection.

What should I tell my health care provider before using Enflonsia?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements your child is using. This will help them know if Enflonsia is right for them.

In particular, make sure that you discuss any of the following.

Heart Surgery. Tell your health care provider if your baby has had heart surgery with cardiopulmonary bypass (a machine that takes over the heart and lung functions during the procedure). After this type of surgery, a child may need to get another dose of Enflonsia to help the medicine work the way it should.

Pregnancy. People who can become pregnant are not usually given Enflonsia.

Breastfeeding. People who can breastfeed are not usually given Enflonsia.

How can I get more information about Enflonsia?

For more information about Enflonsia, you can visit the drugmaker’s website at www.enflonsia.com or call them at 877-888-4231.

Interactions

Does Enflonsia interact with foods or drinks?

There are no known interactions between Enflonsia and foods or drinks.

Does Enflonsia interact with other medicines (drug interactions)?

There are no known interactions between Enflonsia and other medicines. Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements your child is using.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much Enflonsia?

If you or someone else has used too much Enflonsia, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of Enflonsia?

Enflonsia is usually given as a one-time dose by a health care provider in a hospital, clinic, or pediatrician’s office. If you miss an appointment for your child to receive Enflonsia, call to make another appointment as soon as possible.