How effective are the varicella-containing vaccines in preventing varicella disease?
Post-licensure, vaccine-effectiveness studies of one dose of the single-antigen varicella vaccine have shown high levels of protection (70%-90%) against any form of varicella disease and more than 90% protection against severe disease. In the randomized clinical trial of one versus two doses of single-antigen varicella vaccine administered 3 months apart, the estimated vaccine efficacy of two doses was 98%, which was significantly higher than after one dose. The two-dose regimen was 100% efficacious against severe varicella. If a vaccinated person does get varicella, it is usually a very mild case with fewer lesions (usually less than 50, which are frequently not vesicular), mild or no fever, and a quicker recovery. Persons with rash, however, are infectious.
