The Effectiveness of the Varicella Vaccine in Clinical Practice

A varicella vaccine containing live attenuated virus (Oka strain) was developed in Japan in the early 1970s. 1 In the United States, the vaccine was approved by the Food and Drug Administration in 1995 and is recommended for persons 12 months of age or older who are susceptible to chickenpox. 2 There have been numerous questions about both the use and the effectiveness of varicella vaccine. 3 The efficacy of a vaccine as it is used in clinical practice may be different from its efficacy in a clinical trial. 4 Much of the evidence on which the licensure of varicella vaccine was based came . . .