Study setting and population
In August 2011, we began an observational, prospective
cohort study of children at the Queen Sirikit National
Institute of Child Health (QSNICH), the largest public
tertiary care hospital for children, in Bangkok, Thailand.
Children were eligible for enrollment if they were residents of
metropolitan Bangkok, 0–36 months of age, routinely sought
care at QSNICH, and not acutely ill at enrollment. We aimed
to enroll an equal number of healthy children and children
with underlying comorbidities (prematurity/low birth weight
[