Materials and methods . Study design . From October 1, 2020, through January 31, 2021, 346 households in Washington’s (WA) Seattle metropolitan area were enrolled into a longitudinal cohort study. Enrolled households were remotely monitored weekly for symptoms of respiratory illness by an online symptom questionnaire until June 20, 2021. Households with children between 3?months and 17?years of age were recruited from local elementary and middle schools, as well as from a cohort of hous...