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Objective: Each year, influenza and its complications account for 10,000-40,000 excess deaths in the United States. Over 80% of these deaths occur among the elderly. The Advisory Committee on Immunization Practices for the US Public Health Service and others recommend that all persons 65 years of age and older as well as other persons with high-risk conditions receive annual influenza vaccination. Despite these recommendations, 40% or more of high-risk persons fail to receive influenza vaccine. Among the barriers to successful immunization efforts are persistent uncertainties regarding the effectiveness of the vaccine in preventing morbidity and mortality associated with influenza. The purpose of this study was to assess influenza vaccine effectiveness in reducing hospitalization rates for a broad range of influenza-associated complications, in reducing deaths from all causes, and in reducing hospitalization costs among all elderly enrollees of a large health maintenance organization., Methods: A serial cohort study with internal controls was designed. All enrollees, 65 years of age and older, were identified for each of three consecutive vaccination and subsequent influenza seasons for 1990-1991 through 1992-1993. Baseline characteristics and outcome data were collected from computerized, linked, administrative data bases. Outcomes were adjusted for the presence of baseline characteristics including age, gender, high-risk diagnoses, medication refills in high-risk therapeutic classes, and previous health care resource utilization., Results: There were more than 25,000 seniors in each of the three study cohorts. Influenza vaccination rates ranged from 45 to 58%, and vaccinated subjects at baseline appeared to be 'sicker' than nonvaccinated subjects. Influenza vaccination was associated with significant reductions in all outcomes evaluated including outpatient visits (17% reduction in pneumonia and influenza visits, 6.4% reduction in all respiratory condition visits), hospitalizations (51.2% reduction in pneumonia and influenza hospitalizations, 32.5% reduction in all respiratory condition hospitalizations, 28.6% reduction in congestive heart failure hospitalizations), hospitalization costs (30.7% reduction in hospitalization costs for all respiratory conditions and congestive heart failure combined), and deaths from all causes (45% reduction in death from all causes)., Conclusions: Influenza vaccination of elderly persons living in the community is associated with reduced hospitalizations from complications from influenza, with fewer deaths during the influenza season, and with direct health care cost savings. Few, if any, other preventive or therapeutic interventions for adults match or exceed these benefits.

Background: Although influenza causes substantial morbidity and mortality in all age groups, current recommendations emphasize annual immunization for people at high risk for complications of influenza. We conducted a double-blind, placebo-controlled trial of vaccination against influenza in healthy, working adults., Methods: In the fall of 1994, we recruited working adults from 18 to 64 years of age from in and around the Minneapolis-St. Paul area and randomly assigned them to receive either influenza vaccine or placebo injections. The primary study outcomes included upper respiratory illnesses, absenteeism from work because of upper respiratory illnesses, and visits to physicians' offices for upper respiratory illnesses. The economic benefits of vaccination were analyzed by estimating the direct and indirect costs associated with immunization and with upper respiratory illnesses., Results: We enrolled a total of 849 subjects. Baseline characteristics were similar in the two groups. During the follow-up period, consisting of the 1994-1995 influenza season (December 1, 1994, through March 31, 1995), those who received the vaccine reported 25 percent fewer episodes of upper respiratory illness than those who received the placebo (105 vs. 140 episodes per 100 subjects, P < 0.001), 43 percent fewer days of sick leave from work due to upper respiratory illness (70 vs. 122 days per 100 subjects, P = 0.001), and 44 percent fewer visits to physicians' offices for upper respiratory illnesses (31 vs. 55 visits per 100 subjects, P = 0.004). The cost savings were estimated to be $46.85 per person vaccinated., Conclusions: Vaccination against influenza has substantial health-related and economic benefits for healthy, working adults.

Background: Despite recommendations for annual vaccination against influenza, more than half of elderly Americans do not receive this vaccine. In a serial cohort study, we assessed the efficacy and cost effectiveness of influenza vaccine administered to older persons living in the community., Methods: Using administrative data bases, we studied men and women over 64 years of age who were enrolled in a large health maintenance organization in the Minneapolis-St. Paul area. We examined the rate of vaccination and the occurrence of influenza and its complications in each of three seasons: 1990-1991, 1991-1992, and 1992-1993. Outcomes were adjusted for age, sex, diagnoses indicating a high risk, use of medications, and previous use of health care services., Results: Each cohort included more than 25,000 persons 65 years of age or older. Immunization rates ranged from 45 percent to 58 percent. Although the vaccine recipients had more coexisting illnesses at base line than those who did not receive the vaccine, during each influenza season vaccination was associated with a reduction in the rate of hospitalization for pneumonia and influenza (by 48 to 57 percent, P < or = 0.002) and for all acute and chronic respiratory conditions (by 27 to 39 percent, P < or = 0.01). Vaccination was also associated with a 37 percent reduction (P = 0.04) in the rate of hospitalization for congestive heart failure during the 1991-1992 season, when influenza A was epidemic. The costs of hospitalization for all types of illness studied were lower in the vaccinated group during 1991-1992 (range of reduction, 47 to 66 percent; P < 0.005) and for acute and chronic respiratory conditions and congestive heart failure in 1990-1991 (reductions of 37 percent and 43 percent, respectively; P < or = 0.05). Direct savings per year averaged $117 per person vaccinated (range, $21 to $235), with cumulative savings of nearly $5 million. Vaccination was also associated with reductions of 39 to 54 percent in mortality from all causes during the three influenza seasons (P < 0.001)., Conclusions: For elderly citizens living in the community, vaccination against influenza is associated with reductions in the rate of hospitalization and in deaths from influenza and its complications, as compared with the rates in unvaccinated elderly persons, and vaccination produces direct dollar savings.

Concern about side effects constitutes a major deterrent to patient compliance with influenza vaccination, yet there is a paucity of data about the occurrence of adverse reactions in the population targeted for immunization. We conducted a randomized, double-blind, crossover trial to compare the frequency of adverse reactions following administration of 1988-1989 trivalent split-antigen influenza vaccine and saline placebo. Outpatient veterans 65 years of age or over (n = 336) were recruited by mail and were randomly assigned to receive vaccine followed 2 weeks later by placebo injection or placebo followed 2 weeks later by vaccine. There was no significant difference between influenza vaccine and placebo with respect ot the proportion of subjects reporting disability or systemic symptoms.

Purpose: To enhance influenza vaccination rates for high-risk outpatients at the Department of Veterans Affairs Medical Center (VAMC) in Minneapolis, Minnesota, an institution-wide immunization program was implemented during 1987., Patients and Methods: The program consisted of: (1) a hospital policy allowing nurses to vaccinate without a signed physician's order; (2) stamped reminders on all clinic progress notes; (3) a 2-week walk-in flu shot clinic; (4) influenza vaccination "stations" in the busiest clinic areas; and (5) a mailing to all outpatients. Risk characteristics and vaccination rates for patients were estimated from a validated self-administered postcard questionnaire mailed to 500 randomly selected outpatients. For comparison, 500 patients were surveyed from each of three other Midwestern VAMCs without similar programs., Results: Overall, 70.6% of Minneapolis patients were high-risk and 58.3% of them were vaccinated. In contrast, 69.9% of patients at the comparison medical centers were high-risk, but only 29.9% of them were vaccinated., Conclusion: The Minneapolis VAMC influenza vaccination program was highly successful and may serve as a useful model for achieving the national health objective for influenza immunization.