Fig. 1From: Reduction of SARS-CoV-2 intra-household child-to-parent transmission associated with ventilation: results from a case–control studyStudy design of the inclusion of index cases and related controls for the case–control analysis on household contaminationLegend: * The source cases in the household did not participate in the study; †related cases were not included in this analysis; online nationwide study conducted in France between October 2020 and May 2022Back to article page