The RR attributable to WP donations was calculated using the following equation:\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \mathrm{HBsAg}\ \mathrm{new}\ \mathrm{infection}\ \mathrm{rate}=\mathrm{Number}\ \mathrm{of}\ \mathrm{HBsAg}\ \mathrm{positive}\ \mathrm{but}\ \mathrm{anti}-\mathrm{HBc}-\mathrm{negative}/\mathrm{The}\ \mathrm{total}\ \mathrm{number}\ \mathrm{of}\ \mathrm{donations}; $$\end{document}HBsAgnewinfection rate=Number of HBsAg positivebutanti−HBc−negative/The total number of donations;the ratio of HBsAg new infection rate = HBsAg new infection rate of first − time donors over HBsAg new infection rate of repeat donors;\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \mathrm{Incidence}\ \mathrm{rate}\ \mathrm{for}\ \mathrm{HBV}\ \mathrm{infection}=\mathrm{HBsAg}\ \mathrm{new}\ \mathrm{infection}\ \mathrm{rate}/\mathrm{HBsAg}\ \mathrm{yield}\ \mathrm{window}\ \left(44\ \mathrm{days}\right); $$\end{document}Incidence rate forHBVinfection=HBsAgnewinfection rate/HBsAg yield window44days; \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \mathrm{RR}=\mathrm{incidence}\ \mathrm{rate}\ \mathrm{for}\ \mathrm{HBV}\ \mathrm{infection}\times \mathrm{window}\ \mathrm{period}\ \left(0.16\ \mathrm{years}\ \mathrm{or}\ 59\ \mathrm{days}\right); $$\end{document}RR=incidence rate forHBVinfection×window period0.16years or59days;