The studies were each evaluated on six quality indicator criteria (Tables S2 and S3) . First, all studies reported the geographic location of the study, but few, if any, reported more specific information on setting such as altitude and annual rainfall, prevalence of malnutrition and AIDS, or immunization coverage against pneumonia vaccines and access to health care [15] . Second, all but 2 studies (35 [95%] of 37) reported at least one year of data. Third, all studies reported the site of case detection and the age of the cases. Fourth, the population size was not given for 15 (54%) of the 28 mortality studies; when population was reported, at least 50 cases were reported. Fifth, four (22%) of 18 studies of incidence and 27 (97%) of 28 studies of mortality reported quality assurance and monitoring.