VARICELLA-ZOSTER VIRUS (VZV) REACTIVATION IS RELATED TO THE LOW RESPONSE OF VZV-SPECIFIC IMMUNITY AFTER CHICKENPOX IN INFANCY

To clarify the cause of herpes tester in immunocompetent children, specific humoral and cellular immunity was determined using an ELISA and a lymphoproliferative assay, respectively, in infants <1 year of age and children greater than or equal to 1 year ofage who had chickenpox. Thirteen (59.1%) of 22 infants, 17 (81.0%) of 21 children greater than or equal to 1 year of age (P < .02), and 13 (86.7%) of 15 children greater than or equal to 2 years of age (P < .001) had positive varicella-zoster virus (VZY)-specific cellular immunity. VZV-specific antibodies in infants were significantly lower than those in children greater than or equal to 1 year old (P <.01) and greater than or equal to 2 years old (P (.001). The possibility of subclinical reactivation was demonstrated by an increase in the specific cellular or humoral immunity (or both) in all of 6 infants who had negative specific cellular immunity. The low response of specific immunity and the immunologic evidence of reactivation in infants after chickenpox provide a possible explanation for the finding that chickenpox in infancy is a risk factor for herpes tester.