Experience and Reason: Twenty-Year Follow-Up of Protective Immunity of the Oka Strain Live Varicella Vaccine

Abstract

Since the first report on the development of a live attenuated varicella vaccine in 1974, the vaccine has been studied extensively, with largely favorable results, in both healthy and leukemic children. It is now licensed in Japan, Korea, and some European countries, and is being considered for licensure in the United States. Although various clinical trials have established the safety, immunogenicity, and the efficacy of the vaccine, concern has been expressed that waning immunity in the vaccine recipients might allow the occurrence of more severe varicella later in life. We show data relevant to this concern on the approximately 20-year follow-up study of the vaccine recipients; this work further extends the experience of a long-term protective efficacy of the vaccine.