Clinical Data and Sample Collection
Daily symptoms and household isolation measures (e.g. mask use, household separation) were recorded in a standardized diary and disease severity was classified according to WHO criteria 29. Serial samples of saliva, NPS, and stool were self-collected by all family members, every week for one month following the date of the first positive swab of the index case. Blood samples were collected approximately at baseline and 28 days after onset of infection. Data were compiled for each participant, for SARS-CoV-2 (positive/negative), case (index/secondary), symptoms (symptomatic/asymptomatic), stool (positive/negative), saliva (positive/negative), salivary antibodies (positive/negative) and serology (positive/negative) (Supplementary Table 1). The household secondary attack rate was calculated as the total number of secondary cases over the total number of household contacts.