Varicella Virus Vaccine, Live (Oka Strain)

摘要

Children with acute leukemia are at high risk to develop severe or fatal varicella. Available measures such as passive immunization and antiviral chemotherapy have failed to prevent varicella deaths. An alternative approach, vaccination, has been successfully developed in Japan. Over 2000 Japanese have been immunized, including over 100 with malignancy, with only minor side effects. The author is therefore studying the protective efficacy of varicella vaccine in leukemic children. The vaccine is derived from the original Takahashi-Oka strain, isolated from a normal child with chickenpox. The virus was passaged about 30 times in tissue culture. First phase studies in 14 adults revealed no acute toxicity after vaccination and good immunologic responses. Four leukemic vaccines off chemotherapy 2-8 months reacted similarly. No vaccinees shed virus nor were any infectious to others. Three close hospital exposures to varicella occurred among vaccinees; none have developed varicella. The plan to immunize 500 leukemic children with chemotherapy discontinued for two weeks, and follow their immune responses to the vaccine. When these children are exposed closely to varicella (e.g. in their sibs) the efficacy of the vaccine will be tested.