Efficacy of postexposure immunization with live attenuated varicella vaccine in the household setting--a pilot study.

The aim of the present study was to examine the efficacy of postexposure vaccination with Varilrix in the household setting. A randomized, double-blind, placebo-controlled design was used. Twenty-two children received the varicella vaccine and 20, a placebo. The relative risk of developing varicella with a placebo compared with the vaccine was 1.1 (95% confidence interval 0.55-2.21). The risk of developing moderate to severe disease was eight times greater in the placebo group (RR=8), indicating an 80% protective effect against moderate/severe disease. The varicella vaccine Varilrix may not be effective in preventing varicella when administered after household exposure, although it is highly effective in ameliorating the disease in those who acquire it under these circumstances.