Safety of the live, attenuated varicella vaccine in pediatric recipients of hematopoietic SCTs.

VZV is an important cause of morbidity and mortality among patients after hematopoietic SCT (HSCT). There is controversy surrounding the use of the live attenuated varicella vaccine (LAVV) in this population due to concerns that the immunization may cause VZ-related disease. The Blood and Marrow Transplant (BMT) group at the University of California, San Francisco (UCSF) Children's Hospital has been recommending the LAVV for immunocompetent HSCT patients since 1995. We retrospectively examined the incidence of post-immunization complications attributable to the LAVV in pediatric patients after HSCT. We also reported seroconversion rates when possible. Among 68 recipients of the LAVV after HSCT, 3 (4.4%; 95% confidence interval (CI)=1.0-12.7%) experienced mild-to-moderate symptoms potentially attributable to vaccination, and there were no severe reactions. Among 28 patients analyzed for seroconversion, 18 (64.3%; 95% CI=45.8-79.4%) seroconverted, 3 (10.7%; 95% CI 2.9-28.0%) possibly seroconverted and 7 (25.0%; 95% CI=12.4-43.6%) failed to seroconvert. It appears safe to administer the LAVV to immunocompetent patients after HSCT. Prospective studies are needed to more accurately determine rates of vaccine complications, efficacy and immunologic responses to vaccination.