Live attenuated varicella vaccine. Efficacy for children with leukemia in remission

Abstract

One hundred ninety-one varicella-susceptible children with leukemia in remission were immunized with live attenuated varicella vaccine. There was serological evidence of an immune response in .apprx. 80% after 1 dose and in > 90% after 2 doses. The major side effect was mild to moderate rash, seen especially in children with maintenance chenotherapy suspended for 1 wk before and 1 wk after vaccination. Childen with rash had higher antibody titers than those without rash, but those with rash were also at risk (10%) to transmit vaccine virus to others. Twenty-two vaccinees subsequently had household exposure to varicella or zoster. The attack rate of clinical varicella in these vaccines was 18%, significantly lower than the attack rate of .apprx. 90% in varicella-susceptible persons with household exposures. All cases of clinical illness were extremely mild, an average of .apprx. 50 vesicles. The mild character of the illness was clearly different than varicella in unimmunized children receiving chemotherapy for leukemia. Varicella vaccine was .apprx. 80% effective in preventing clinical varicella in children with leukemia and completely effective in preventing severe varicella in this high-risk group.