A total of 86,000 deaths in excess of the normally expected number occurred in the United States as a result of the 3 epidemic prevalences of influenza in the period 1957-1960. It was deemed important to characterize these 86,000 excess deaths further in order to define, as accurately as possible, those individuals at highest risk of death from influenza. The high-risk groups were demonstrated to be persons over 65 years of age, persons with certain associated chronic diseases, particularly cardiovascular disease and broncho-pulmonary disease, and pregnant women. It may be anticipated that some benefit, in terms of saving of lives, would accrue if these high-risk groups were routinely immunized against influenza.
Eickhoff TC, Sherman IL, Serfling RE. Observations on Excess Mortality Associated with Epidemic Influenza. JAMA. 1961;176(9):776–782. doi:10.1001/jama.1961.03040220024005