Force of infection by age and sex.

The event is inferred seroconversion based either on fold change, or change from below to above the absolute threshold. The person-years includes time between donations, and also from an inferred negative value to the first donation. In order to estimate the force of infection, periods after the first positive result for each person are not included, on the basis of not being at risk. People with missing age or sex are not included. Note that the overall rate cannot be obtained by simple division of the events and person-years between donations, because the exact times of the events were not observed.本研究中的事件为基于倍数变化，或从低于绝对阈值升至高于绝对阈值所推断出的血清转换（seroconversion）。人年（person-years）统计范围涵盖两次献血之间的时长，以及从推断为阴性的阶段至首次献血的时长。为估算感染压力（force of infection），每位受试者首次检测呈阳性结果后的时段因不再处于感染风险中，故未被纳入统计。年龄或性别信息缺失的受试者未被纳入研究。需注意：由于事件发生的确切时间未被观测记录，无法通过简单地用事件总数除以两次献血间的人年数来得到整体发生率。