Immunization of children with acute lymphoblastic leukemia with live attenuated varicella vaccine without complete suspension of chemotherapy.

A total of 44 children with acute lymphoblastic leukemia were immunized against chickenpox with the Oka/Merck strain live attenuated varicella vaccine. Of these children, 24 continued oral chemotherapy with 6-mercaptopurine during the immunization period and 20 had suspension of all chemotherapy for 1 week before and 1 week after the vaccine. Seroconversion, as determined by the detection of fluorescent antibody to membrane antigens, occurred in 91% and did not differ between patients continuing 6-mercaptopurine from those in whom chemotherapy was suspended. Fever and/or rash occurred in less than one third of vaccinated children. Unexpected reactions occurred in two vaccinated children, one from each group, both of whom had low absolute lymphocyte counts (less than 750/microL) on the day of immunization. Vaccine-induced immunity appeared effective in preventing or modifying chickenpox after exposure to natural disease.