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during influenza A epidemics which occurred in the United States between 1970-78 were computed utilizing unpublished data from the National Hospital Discharge Survey (NHDS).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influenza upon health and health services, much of which may be preventable, and illustrates an important use of unpublished data contained in the NHDS.