This serial cohort study assessed the risk of hospitalization or death associated with influenza and the effectiveness of influenza vaccination among subgroups of elderly members of 3 managed-care organizations in the United States. Data on baseline characteristics and outcomes were obtained from computerized databases. A total of 122,974 (1996-1997 season) and 158,454 (1997-1998 season) persons were included in the cohorts. Among unvaccinated persons, hospitalizations for pneumonia/influenza or death occurred in 8.2 of 1000 healthy and 38.4 of 1000 high-risk persons in year 1, and in 8.2 of 1000 healthy and 29.3 of 1000 high-risk persons in year 2. After adjustments, vaccination was associated with a 48% reduction in the incidence of hospitalization or death (95% confidence interval [CI], 42-52) in year 1 and 31% (95% CI, 26-37) in year 2. Effectiveness estimates were statistically significant and generally consistent across the healthy and high-risk subgroups. The absolute risk reduction, however, was 2.4- to 4.7-fold higher among high-risk than among healthy elderly persons. All elderly individuals may substantially benefit from vaccination. However, the impact of influenza is greater in persons with high-risk medical conditions.

Surveillance data on nonpolio enterovirus (NPEV) from the Centers for Disease Control (Atlanta, Georgia) for the United States from 1970 to 1983 were analyzed for the temporal and geographic patterns of the most common types of NPEV isolated. The number of isolates varied from year to year, partly because of variation in the number of reporting laboratories and partly because of true variation in the rate of isolation. The most common types isolated also varied from year to year, yet the 15 most common types over the entire 14-year period accounted for 65%-89% of isolates for a given year. The 15 most common types of NPEV had two basic patterns of isolation, one in which a type had periodic epidemic years and the other in which it did not. In 11 of the 14 years there was one or more epidemic types, each accounting for greater than or equal to 20% of all isolates of NPEV that year. The six most common isolates in March, April, and May predicted an average of 59% of the total isolates detected in July-December of that year.

This study developed methods and determined the impact of influenza vaccination on elderly persons in 3 large health plans: Kaiser Permanente Northwest, HealthPartners, and Oxford Health Plans. Data for the 1996-1997 and 1997-1998 seasons were extracted from administrative databases. Subjects were health plan members > or = 65 years old. Comorbid conditions collected from the preceding year were used for risk adjustment with logistic regression. The virus-vaccine match was excellent for year 1 and fair for year 2. Both years, during peak and total periods, vaccination reduced all causes of death and hospitalization for pneumonia and influenza: hospitalizations were reduced by 19%-20% and 18%-24% for years 1 and 2, respectively, and deaths were reduced by 60%-61% and 35%-39% for the same periods. These results show that all elderly persons should be immunized annually for influenza. The methods used in this study are an efficient cost-effective way to study vaccine impact and similar questions.

Background: This paper presents the results of systematic reviews of the effectiveness, applicability, other effects, economic impact, and barriers to use of selected population-based interventions intended to improve vaccination coverage. The related systematic reviews are linked by a common conceptual approach. These reviews form the basis for recommendations by the Task Force on Community Preventive Services (the Task Force) regarding the use of these selected interventions. The Task Force recommendations are presented on pp. 92-96 of this issue. Medical Subject Headings (MeSH):vaccine-preventable diseases, vaccination coverage, community health services, decision-making, evidence-based medicine, systematic reviews, population-based interventions, practice guidelines, preventive health services, public health practice, task force. Introduction V accine-preventable diseases among children, adolescents, and adults represent major continuing causes of morbidity and mortality in the United States. During the latter half of the twentieth century, the success of childhood vaccination programs in the United States has led to a Ͼ95 % decline in most vaccine-preventable diseases of childhood. However, Ͼ400,000 cases of illness and Ͼ30,000 deaths caused by vaccine-preventable diseases still occur each year 1 (CDC unpublished data).Diphtheria, invasive Haemophilus influenzae type b (Hib) disease, measles, poliomyelitis, rubella, tetanus, mumps, varicella, and pertussis are typically referred to as vaccine-preventable diseases of childhood. Vaccinations primarily indicated for adults include influenza, pneumococcal, and hepatitis B. However, during the 1990s, the distinction between childhood and adult vaccine-preventable diseases became less clear. Many childhood vaccine-preventable infections, including measles and pertussis, are found increasingly among adults, 2,3 and hepatitis B vaccinations are now routinely recommended for infants and adolescents. Table 1 outlines universally recommended (i.e., vaccinations recommended for most or all persons in certain age groups) vaccinations for children, adolescents, and older adults.In children, Ͼ50,000 cases of varicella occur each year, making that disease the most common vaccinepreventable disease among children 4 ; in adults, influenza, pneumococcal disease, and hepatitis B are all still common vaccine-preventable diseases, with hundreds of thousands of cases occurring each year.5 Mortality attributable to vaccine-preventable diseases is still substantial. Each year, approximately 500 persons in the United States die of childhood vaccine-preventable diseases, and Ͼ30,000 adults die of influenza, pneumococcal infections, and hepatitis B.1 Influenza, which accounts for an average of 20,000 deaths/year, is usually the largest killer. 5The effectiveness of universally recommended vaccinations in preventing disease for adults, adolescents, and children is well-established. 6 -14 In addition to protecting individuals from diseases passed from person to person contact, vaccinat...