Our current understanding of pneumonia etiology was largely developed from research studies in the 1970s through the early 1990s. These findings showed that the majority of fatal pneumonia cases in children is due to 2 bacteria—Streptococcus pneumoniae and Haemophilus influenzae type b (Hib)—and that these deaths occurred primarily in communities with high levels of child mortality, typically impoverished settings that lack access to basic healthcare such as antibiotics and oxygen therapy .