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Fig. 1 | Emerging Themes in Epidemiology

Fig. 1

From: Mitigation of biases in estimating hazard ratios under non-sensitive and non-specific observation of outcomes–applications to influenza vaccine effectiveness

Fig. 1

Occurrence of true and false-positive influenza events. The figure shows the eight possible paths of events for a study subject during the study period (influenza season). The true event is depicted either by a white circle if it was recorded or by a crossed circle if it was not recorded. False-positive events are depicted by black circles. Although false positives may occur repeatedly, the figure shows only the first of these if any. The subject’s true time at risk during the study period is marked by a solid line. In the study, the subject’s follow-up (dashed line) ends at the time of the first recorded event, which is highlighted by a square around the event-defining circle, or at the time of censoring (vertical bar). Although recorded, the true event is not part of the data under study if there is a preceding false-positive event. The true at-risk time is then underestimated (Paths 2, 5 and 8). By contrast, Paths 6 and 7 show scenarios in which the true at-risk time is overestimated

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