Chickenpox (varicella)

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Chickenpox is a common, highly contagious viral infection caused by an organism known as varicella-zoster virus. The incubation period ranges from one to three weeks. Symptoms include fever, malaise, body aches, sore throat, headache, and a distinctive rash consisting of tiny blisters (vesicles) all over the body. Cases of chickenpox remain infectious until the skin lesions crust over, usually five to seven days after they appear. Complications may include pneumonia, hepatitis, encephalitis, and bacterial skin infections. Chickenpox may be treated with acyclovir, famcyclovir, or valacyclovir, but mild cases in children usually require no treatment except analgesics, antihistamines, and baths for relief of pain and itching.

Varicella vaccine (Varivax; Merck and Co., Inc) (PDF) consists of a weakened strain of varicella-zoster virus. In adults, a complete series consists of two doses separated by one to two months. In children, a single dose is sufficient. The vaccine is recommended for international travelers who are not immune to chickenpox. Many people who believe they never had chickenpox in fact have antibodies to chickenpox in their blood, probably as a result of a childhood case that was so mild that it was never diagnosed. Checking for chickenpox antibodies before receiving the vaccine is therefore a reasonable option for travelers with no history of the disease.

The most common adverse reaction to the vaccine is pain or swelling at the injection site. Occasionally, recipients of the vaccine develop a mild varicella-like illness. Rarely, mild cases of shingles (zoster) have been reported. Anyone with a history of allergy to gelatin, neomycin, or a prior dose of varicella vaccine should not receive the vaccine. Because the vaccine contains live virus, it should not be given to pregnant women or those who are immunosuppressed due to malignancies, immune deficiency disease (including HIV), or immunosuppressive medications. Because of the association between aspirin use and Reye syndrome following chickenpox, aspirin and other salicylates should be avoided for 6 weeks after receiving varicella vaccine.

From the World Health Organization (WHO)

Varicella vaccines (WHO position paper)

Varicella vaccine (background)

From the Centers for Disease Control (CDC)

Varicella (Chickenpox)

Varicella

Varicella fact sheet

Prevention of varicella: recommendations of the Advisory Committee on Immunization Practices(PDF)

Prevention of varicella: updated recommendations of the Advisory Committee on Immunization Practices

From Health Canada

Update on Varicella

Statement on Recommended Use of Varicella Virus Vaccine

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