Varicella (commonly known as chickenpox) is a common childhood disease that causes fever, skin rash, and a breakout of fluid-filled blisters on the skin.

Varicella virus vaccine is used to help prevent this disease in adults and children who are at least 12 months old.

This vaccine works by exposing you to a small dose of the virus or a protein from the virus, which causes the body to develop immunity to the disease. This vaccine will not treat an active infection that has already developed in the body.

Like any vaccine, varicella virus vaccine may not provide protection from disease in every person.

You should not receive a booster vaccine if you had a life-threatening allergic reaction after the first shot. You should also not receive this vaccine if you have any illness with fever, active tuberculosis that is not being treated, or a weak immune system.

You should not receive this vaccine if you are pregnant. Use effective birth control to prevent pregnancy for 3 months after receiving a varicella vaccine.

This vaccine is given as an injection (shot) under the skin or into a muscle. You will receive this injection in a doctor's office, clinic setting, or pharmacy.

Any person who has never had chickenpox or received this vaccine should get 1 or 2 doses of varicella vaccine.

Children from 1 to 12 years old should receive 2 doses. The booster dose may be given at least 3 months after the first, but may be delayed until the child is 4 to 6 years old.

People who are at least 13 years old and have never had chickenpox or received a varicella vaccine should receive 2 doses 4 to 8 weeks apart.

Your individual booster schedule may be different from these guidelines. Follow your doctor's instructions or the schedule recommended by your local health department.

This vaccine can cause false results on a skin test for tuberculosis for up to 6 weeks. Tell any doctor who treats you if you have received a varicella virus vaccine within the past 4 to 6 weeks.

You should not receive this vaccine if you are allergic to gelatin or neomycin, or if you have ever had a life-threatening allergic reaction to any vaccine containing varicella.

You should also not receive this vaccine if you have:

• fever;

• active tuberculosis that is not being treated;

• severe immune suppression caused by disease (such as cancer, HIV, or AIDS), or by receiving certain medicines such as steroids, chemotherapy or radiation; or

• if you are pregnant or plan to become pregnant in the next 3 months.

May cause birth defects. Do not receive varicella vaccine if you are pregnant. You must use effective birth control for at least 3 months after your last dose. Tell your doctor if you become pregnant.

Tell your doctor if:

• you have a weak immune system;

• someone in your household has a weak immune system; or

• you have recently had a blood transfusion or have received an immune globulin or other blood products.

Ask a doctor if it is safe to breastfeed while using Varivax.

Be sure to receive all recommended doses of this vaccine or you may not be fully protected against disease.

An overdose of this vaccine is unlikely to occur.

For at least 6 weeks after receiving a varicella vaccine, avoid coming into contact with newborn infants, pregnant women who have never had chickenpox, and anyone who has a weak immune system. There is a chance that you could pass the virus to a person with a weak immune system or no immunity to chickenpox.

Get emergency medical help if you have signs of an allergic reaction (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

You should not receive a booster vaccine if you had a life-threatening allergic reaction after the first shot. Keep track of any and all side effects you have after receiving this vaccine. When you receive a booster dose, you will need to tell the doctor if the previous shot caused any side effects.

Varivax may cause serious side effects. Call your doctor at once if you have:

• walking problems;

• seizures;

• severe skin problems or skin infection;

• fever, chills, cough with mucus, chest pain, feeling short of breath;

• stiff neck, light sensitivity;

• confusion;

• easy bruising, purple or red spots under your skin; or

• sudden numbness or weakness on one side of the body, problems with vision or speech, pain or swelling in one leg.

Common side effects include:

• irritability;

• fever;

• rash that looks like chickenpox; or

• redness, itching, pain, or swelling where the shot was given.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report vaccine side effects to the US Department of Health and Human Services at 1-800-822-7967.

For anyone under 18 years old: Do not take a salicylate medicine (such as aspirin, Kaopectate, Pepto-Bismol, and others) for at least 6 weeks after receiving a varicella virus vaccine. Salicylates can cause Reye's syndrome, a serious and sometimes fatal condition in children or teenagers with chickenpox, and the varicella virus in this vaccine exposes you to a small amount of this virus.

Other drugs may affect this vaccine, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all other medicines you use.