Recommendations for the use of live attenuated varicella vaccine. American Academy of Pediatrics Committee on Infectious Diseases.

VARICELLA AND ZOSTER Varicella-zoster virus (VZV) is the cause of two diseases, varicella (chickenpox), which is a primary infection, and zoster (shingles), a secondary infection caused by reactivation of latent VZV.1 In the United States, vancella is typically an ifiness of children under the age of 10 years; 5% to 10% of adults remain susceptible. Varicella is a systemic infection that stimulates development of antibodies and cell-mediated immunity (CMI); second episodes in healthy persons are unusual. Varicella in otherwise healthy children is usually a self-limited disease characterized by fever, malaise, and a generalized vesicular pruritic rash of approximately 250 to 500 vesicles that usually lasts about 5 days. Varicella is a characteristic disease that is easily recognized. A history of varicella infection is associated with positive serologic findings for VZV antibodies in >95% of individuals. Serologic tests include enzyme immunoassay (EIA), latex agglutination (LA), indirect fluorescent antibody, and fluorescent antibody membrane antigen assays. These tests are reliable in determining immune status in healthy persons but may not be as reliable in determining the immune status of immunocompromised persons in whom a positive but low titer may not correlate with protection.2 The complement fixation test is not sensitive enough to be reliable in determining susceptibility in any child. In children and adults with a history of varicella, antibody testing generally is not necessary to establish immune status. Those under the age of 18 years without a history of varicella are probably susceptible to infection. In persons over 18 years of age, even with no history or an unknown history of varicella infection, >70% have been infected, resulting in positive serologic findings. Therefore, in these older individuals, determination of immune status before considering VZV immunization may be cost-effective. During varicella the VZV gains access to sensory