THE EFFECTIVENESS OF INFLUENZA VACCINATION

在过去的几十年里，每年接受流感疫苗接种的老年人的比例急剧增加，从20世纪70年代末的20%增加到1996年的65%以上。尽管出现了这种急剧增长，但在按服务收费的医疗保险受益人中，肺炎和流感住院率并没有下降，事实上，从1986年的每1 000名受益人15.5人增加到1996年的每1 000名受益人20.1人。这一观察结果对最近几项大规模研究中检测到的流感免疫对P&I住院的40%-70%保护作用提出了挑战。由于流感疫苗在生物学上不可能引起肺炎或流感，其他因素必须解释这种自相矛盾的关系。本研究的目的是发现这些其他因素。本研究将探讨以下研究问题：1。哪些免疫学因素--包括疫苗效力低、病毒-疫苗匹配差以及对高危人群的针对性差--可以解释流感免疫接种率与肺炎和免疫接种住院率之间明显的异常关系？2.医疗保险受益人进入管理式医疗机构的有利选择是否在收费服务部门P&L住院率的矛盾增长中发挥了作用？3.医疗保健市场因素，如减少医院普查和”管理式医疗“溢出”效应，有助于解释P&L住院的矛盾增长？

Over the past decades, the percentage of elderly individuals who receive annual influenza immunization has increased dramatically, from 20% in the late 1970s, to over 65% in 1996. In spite of this dramatic increase, the rate of hospitalization for pneumonia and influenza (P&I) among fee-for-service Medicare beneficiaries has not decreased, and has in fact increased fairly consistently from 15.5 per 1000 beneficiaries in 1986 to 20.1 per 1000 in 1996. This observation challenges the 40%-70% protective effect of influenza immunization against P&I hospitalizations detected in several recent, large scale studies. Because it is biologically impossible for influenza vaccines to cause pneumonia or influenza, other factors must account for this paradoxical relationship. The purpose of this study is to discover these other factors. The following research questions will be explored: 1. What immunological factors--including low vaccine efficacy, poor virus-vaccine match, and poor targetting of at-risk individuals-- account for the apparent anomalous relationship between influenza immunizations rates and hospitalization rates for pneumonia and immunization? 2. Does favorable selection of Medicare beneficiaries into managed care organizations play a role in the paradoxical increase in P&l hospitalizations in the fee-for-service sector? 3. Do health care market factor-such as reduced hospital censuses and" managed care "spill-over" effect-help explain the paradoxical increase in P&l hospitalizations?