Some countries and/or regions have low prevalence of HBV infections, such as Canada and Hong Kong. These two locations exhibit low residual risks of 1:1,700,000  and 1:22,000 , respectively, whereas China has a moderate-to-high residual risk for HBV infections (about 1:13,670 in Shanghai) . Although the prevalence of HBsAg in the Chinese population has dropped to 7.2% in 2006 from 9.8% since the implementation of the nationwide HBV vaccination program in 1992, the prevalence of HBV infections in China is still high [7, 8, 13, 18]. Continued efforts are still needed in donor education, improving donor recruitment and screening strategies. The incidence window period model used in this study can also be used to evaluate the potential impact of HBV NAT implementation by calculating the expected percentage residual risk reduction and yield of a particular assay system . Per the request of the Chinese Ministry of Health, NAT testing for HBV, HCV, and HIV will have been piloted in all provincial blood centers by 2015 . This may decrease the residual risk of TT-HBV markedly.