The varicella vaccine helps protect against chickenpox (varicella), a very contagious infection caused by the varicella-zoster virus. It causes an itchy rash that looks like small blisters with a red base. In some people, the brain, lungs, and heart can become infected, resulting in serious illness or death. The virus remains in the body after the illness has resolved. If it is reactivated, it can cause shingles years later.
For more information, see the Centers for Disease Control and Prevention's (CDC) Chickenpox vaccine information statement.
(See also Overview of Immunization.)
Vaccination against varicella is part of the routine vaccination schedule recommended for children. The vaccine is given as an injection under the skin. Two doses are given: at age 12 to 15 months and at age 4 to 6 years. It is also recommended for all adolescents and adults who have not had the vaccine or the disease. It is given to them in two doses 4 to 12 weeks apart.
Certain conditions may affect whether and when people are vaccinated (see also CDC: Who Should NOT Get Vaccinated With These Vaccines?). If people have a temporary illness, doctors usually wait to give the vaccine until the illness resolves.
Because the vaccine contains live virus, it is not given to pregnant women, people with a weakened immune system, or people with cancer of the bone marrow or lymphatic system.
The varicella vaccine is very safe, and common side effects are mild. They include pain, swelling, and redness at the injection site and fever and temporary joint pain and stiffness.
Very occasionally, a chickenpox-like rash develops. People who develop this rash after the vaccine should diligently avoid contact with people who have a weakened immune system until after the rash resolves.
Taking aspirin and related drugs (salicylates) after vaccination can cause a rare but serious disorder called Reye syndrome in children under 16 years old. Thus, such children should not be given these drugs for 6 weeks after vaccination.