Varicella-like illness caused by live varicella vaccine in children with acute lymphocytic leukemia.

A varicella-like illness occurred in five of 52 children with acute lymphocytic leukemia following the administration of live varicella vaccine. Only one of the children required treatment with acyclovir. Virus isolated from two of the children was "vaccine-like" but differed slightly from the original vaccine strain when tested by restriction enzyme analysis. There did not appear to be a reversion to virulence because two of the household contacts who seroconverted had mild or subclinical infections. Vaccinees in whom this reaction developed tended to have a poor cellular immune response to varicella-zoster virus.