Figure 1. Mortality rate attributable to either pneumonia or influenza among children aged less than 5 years in the United States, 1900–1960.

The combined annual rates of death per 1,000 child years from either pneumonia or influenza were compiled from U.S. government reports and stratified into two age groups (6, 7). Improvements in the rates of mortality from either pneumonia or influenza before the introduction of antibiotics were associated with major interventions to improve infant feeding and nutrition and with improved housing and reduced indoor air pollution.