Experience with live attenuated varicella vaccine (Oka strain) in healthy Japanese subjects; 10-year survey at pediatric clinic

Live attenuated varicella vaccine (Oka strain, Biken Institute, Osaka, Japa n) was administered to 973 healthy individuals over a 10-year period (1987- 1997) at the pediatric clinic of Showa Hospital in Japan. We evaluated the relevant serological and clinical data, which were collected by questionnai re. Seroconversion by the immune adherence hemagglutination method was docu mented in 94% (805/860) of the initially seronegative subjects. Of the init ially seropositive subjects, 56% (63/113) showed enhancement of antibody af ter vaccination. Reactions to the vaccine were generally insignificant, exc ept for a rash at the injection site, seen in the first 3 days post-adminis tration in 17% (41/241) of the recently vaccinated subjects. In March 1998, we conducted a survey of 559 of the initially seronegative subjects who ha d received the vaccine 0.6-10.8 (mean 5.4) years earlier. Of these subjects , 21% (119/559) contracted breakthrough varicella. However, their symptoms were milder than those caused by natural varicella seen in unvaccinated chi ldren. Seroconversion was demonstrated in 92% (109/119) of these cases. The incidence of breakthrough disease decreased with a rise in postvaccination antibody titer to greater than or equal to 32. Four of the subjects (0.7% of 559) developed herpes tester following vaccination, two of whom had earl ier exhibited breakthrough varicella. Lesions in one case of tester, withou t breakthrough varicella, appeared on the cervical dermatome at the injecti on site. The vaccine was safe and effective. However, there was a relativel y high incidence of rash at the injection site with certain lot numbers use d in recent years which warrants investigation. (C) 2000 Elsevier Science L td. All rights reserved.