The Merck Oka strain varicella vaccine was licensed for use in March, 1995. Beginning in May, 1995, KPVSC has begun a 15 year post-marketing study to evaluate the safety and long term effectiveness of the vaccine. The evaluation includes serial cross-sectional surveys to evaluate the impact of vaccine on varicella disease, 15 year follow-up of a vaccinated cohort for break-through disease, and an assessment of safety through rates of events resulting in emergency and hospital utilization. We report here on safety data in recipients 1-7 years of age Overall there were 67 hospitalizations and 465 emergency visits. Rates in recipients 0-21 days s/p vaccine were compared to the same children 22-30 days s/p vaccine. Cases of hives noted above occurred at 1, 2, 5, 7, 17, 18, 19 & 19 days s/p vaccine. Review of hospitalizations revealed no statistical differences between any diagnostic category. There have been no cases of ataxia in the follow-up period.Table

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Overall, the varicella vaccine appears safe. We have observed a trend of a possible association of hives 2-3 weeks following vaccination. Follow-up is ongoing and updated data will be reported. (Funded by a grant from Merck Research Labs)