Sources of information:
To estimate the incidence and mortality of each outcome needed to estimated YLD and YLL, we performed a systematic review of evidence. This search was performed in February 2020 and was limited to the published primary literature in the English or Spanish language, human subjects, and infant (birth to 5 years). The following engines were searched for the periods specified: MEDLINE from 1950 on, EMBASE from 1974 on, BIREME from 1980 on. To avoid missing any articles published we performed a search using Google search engine and we reviewed the first 100 results returned. The search terms used were: Colombia, infants, acute bronchiolitis, incidence, or mortality. All potentially relevant references were reviewed independently and selected relevant publications. This information was complemented with information on lower tract respiratory diseases (LTRI) in infants younger than 2 years of age, reported to the national epidemiological surveillance system (SIVIGILA) (10). The mortality data was validated with the data reported by the National Department of Statistics - DANE during the same period. Informed consent was not required because we used surveillance data without personal identifiers(11).
We estimated YLL by multiplying the number of AB deaths in infants under 2 years by the number of years of expected remaining life at the age of death according to reference life tables of the global burden of disease study (12). Next, the YLD was obtained by multiplying the number of AB cases in an infant under 2 years by both the average duration of AB obtained from the literature (7, 13-17), and a disability weight that reflected the severity of AB on a scale from 0 (perfect health) to 1 (death) derived from the 2015 Global Burden of Disease study,table 1 .