The residual risk (RR) is different with different blood screening strategies. Using NAT for donor screening can shorten the window period and identify occult HBV infections (OBI) which cannot be detected by HBsAg tests . In terms of the risk for TT-HBV, it is a problem particularly in the countries and/or areas with both a high prevalence of HBV and where NAT for HBV is not used routinely for donor screening . Despite the implementation of donor screening by NAT, there are still a number of countries where there is a residual risk for TT-HBV [9–11].