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Varicella (Chickenpox)

What is varicella?

Varicella (chickenpox) is a very common childhood disease. It is usually mild, but can be serious, especially in young infants and adults. Varicella is caused by the varicella-zoster virus (VZV), a form of the herpes virus. Varicella is a highly contagious virus that is spread from person-to-person through the air or by contacting the fluid from the blisters caused by the virus. Chickenpox causes a blistering itching rash (pox), fever, and fatigue. It can lead to more serious illness including severe skin infection, scars, pneumonia, brain damage, and death.

Immunization against chickenpox

Immunization with the chickenpox vaccine can prevent chickenpox in most people. If a person contracts chickenpox after getting the vaccine, he or she will usually have a very mild case.

When is chickenpox vaccine given?

In the past, more than 90 percent of adult Americans had been infected with chickenpox. Since 1995, a chickenpox vaccine has been available for children 12 months of age and older. Adolescents and adults who have never had chickenpox can also get the vaccine. The vaccine has proven very effective in preventing severe chickenpox. The CDC Advisory Committee on Immunization Practices, the American Academy of Pediatrics, and the American Academy of Family Physicians recommend that all children be vaccinated with the chickenpox vaccine between 12 and 18 months of age. A second dose is recommended at age 4 to 6 years, generally given at the same time as other required preschool vaccinations. 

Many schools now require vaccination prior to entry into preschool or public schools. Catch-up immunization may be given as needed between the ages of seven to 18 years, and to adults.

Children who are sick with another illness or have a fever should wait until they are well to receive the chickenpox vaccine. Some children should not receive the chickenpox vaccine. These include children who have ever had an allergic reaction to gelatin, the antibiotic neomycin, and children who have had a previous reaction to chickenpox vaccine. Your child's doctor will advise you on the vaccine in these and other situations.

What are the risks from chickenpox vaccine?

A vaccine, like any medication, is capable of causing serious problems, such as severe allergic reactions. The risk of chickenpox vaccine causing serious harm or death is very small. Most people who get the chickenpox vaccine do not have any problems with it. Problems may include:

  • Soreness or swelling in the location where the shot was given

  • Fever

  • Mild rash, up to one month after vaccination

Other problems such as low blood count, pneumonia, seizures, and severe brain reactions are very rare. Experts are not sure whether these are caused by the chickenpox vaccine or not.

How do I care for my child after immunization with chickenpox vaccine?

  • Give your child aspirin-free pain reliever, as directed by your child's doctor. Do not give aspirin.

  • An allergic reaction would most likely occur within a few minutes to a few hours of the shot. Signs of an allergic reaction may include difficulty breathing, wheezing (squeaking sounds while breathing due to tight airways), weakness, fast heartbeat, hives, and paleness. Report these or any other unusual signs immediately to your child's doctor.