Hospital-based pneumococcal immunization. Epidemiologic rationale from the Shenandoah study

To explore the potential usefulness of a strategy of hospital-based pneumococcal immunization, we studied a population-based linked record of hospital discharges for Medicare enrollees living in the Shenandoah region of Virginia. A retrospective study of 1633 persons discharged with pneumonia in 1983 showed that 61% to 62% had been discharged within the previous 4 years. Among these patients, 87% had had one or more high-risk conditions recognized during previous hospital admissions. A cohort study demonstrated that discharged patients had a 6% to 9% probability of readmission with pneumonia within 5 years. Each such readmission could be prevented by immunizing few (approximately 100) discharged patients with pneumococcal vaccine. Furthermore, the costs of vaccination would be approximately one-third the costs of hospital care for unvaccinated discharged patients readmitted with pneumonia. These results provide an epidemiologic rationale for current recommendations that elderly patients discharged from hospitals should be immunized with pneumococcal vaccine.