Household Transmission Investigation: Design, Reporting and Critical Appraisal.

Household transmission investigations (HHTI) contribute timely epidemiologic knowledge in response to emerging pathogens. HHTIs conducted in the context of the COVID-19 pandemic in 2020-21 reported variable methodological approaches, producing epidemiological estimates that vary in meaning, precision, and accuracy. Since specific tools to assist with the optimal design and critical appraisal of HHTIs are not available, the aggregation and pooling of HHTI to inform policy and interventions may be challenging. In this manuscript, we discuss key aspects of the HHTI design, we provide recommendations for the reporting of these studies, and propose an appraisal tool that contributes to the optimal design and critical appraisal of HHTI studies. The appraisal tool consists of 12 questions that explore 10 aspects of HHTIs and can be answered ‘yes’, ‘no’ or ‘unclear’. The manuscript seeks to fill a gap in the epidemiologic literature and contribute to standardise HHTI approaches across settings, to achieve richer and more informative datasets. The manuscript also calls for a periodic revision of HHTI protocols and critical appraisal tools