Each household in the cohort was visited soon after delivery to obtain baseline information on demography, socio-economic indicators, health-seeking behaviour, environment, diet and the delivery and birth. Socio-economic status was assessed on a five-point scale modified from the Kuppuswamy scale6 and hygiene on a 24-point scale.7 (link)
After birth, fieldworkers visited each household twice weekly and observed the study child. They interviewed the caregiver about any illness on each day since the last visit. Field workers were trained to use standard definitions to identify common morbidities, and to refer infants when they had any concerns about the child’s health. Mothers were encouraged to bring the infant to the clinic for any illness they felt might be serious. Any child who needed hospital admission was referred to CHAD or CMC as necessary. Physicians at these hospitals managed these children as per their routine practice. The costs of care were borne by the study. Visits to any other health facility and physician-based diagnoses for each visit were recorded. The data collected by field workers were validated in a 10% random subsample on revisits by the study supervisor and/or the physician.
For the analyses, morbidity was classified into broad categories. Gastrointestinal illnesses were defined as diarrhoea (three watery stools in a 24 h period) or vomiting lasting for at least 24 h, respiratory illnesses as runny nose or cough either with or without fever lasting at least 72 h, and undifferentiated fever as fever not associated with other symptoms lasting at least 48 h. Lower respiratory tract infection included bronchitis or pneumonia as diagnosed by the study physician and confirmed by a paediatrician. A new episode of gastrointestinal illness was defined if it occurred at least 48 h after the last episode. The interval for new episodes was 72 h for the other categories.8 (link)
9 (link)