Postlicensure Safety Surveillance for Varicella Vaccine

Abstract

In March 1995, the Food and Drug Administration (FDA) licensed a live virus varicella vaccine (Varivax; Merck & Co, Inc) to prevent chickenpox. Authoritative recommendations^1-3 for nearly universal use of the new vaccine reflected the magnitude of morbidity and mortality due to varicella: 4000 to 9000 hospitalizations and 100 deaths per year from serious secondary infections or central nervous system and other complications.^4,5 The FDA based licensure on studies of safety and efficacy for varicella prevention in almost 9500 healthy children and more than 1500 adolescents and adults.⁶ Usually well tolerated,^7-12 varicella vaccine protects most recipients against primary chickenpox, and most breakthrough cases are mild.^13-15 Adverse events identified before licensure included injection site pain and erythema and a generalized varicella-like rash in 4% to 6% of vaccinees, usually appearing 5 to 26 days after the first dose.¹⁶