Excess pneumonia and influenza associated hospitalization during influenza epidemics in the United States, 1970-78.

In this study, excess rates of pneumonia and influenza (P&I) associated hospitalization during influenza A epidemics which occurred in the United States between 1970-78 were computed utilizing unpublished data from the National Hospital Discharge Survey (NHDS). Excesses occurred at rates of 35, 93, and 370 per 100, 000 persons per epidemic for age groups 15-44, 45-64, and 65+ years. There was no evidence of a persisting excess or a compensatory decline in P&I hospitalization during post-epidemic months. An average excess of about 172, 000 hospitalizations per epidemic at a cost in excess of 300 million was computed. The study quantifies a major impact of epidemic influenza upon health and health services, much of which may be preventable, and illustrates an important use of unpublished data contained in the NHDS.