This study may underestimate the incidence of HBV infections due to its definition of an infection incident and because its risk estimates do not take into account the risk from OBI. The numbers of HBsAg positive and anti-HBc negative tests in each region are low, leading to a general lack of precision in RR calculations (see the wide 95% CIs). In terms of limitations, the incidence calculations are sensitive to assumptions around the window period. In addition, the study may have a number of other limitations around window period estimates. Although, this study included six different locations of blood centers from a diversity of geographical areas, it still may not be representative of all of China.