流行性感冒疫苗符合成本效益,但在成人未被适当使用


  8月15日的《Clinical Infectious Disease》杂志与8月20日的《Annals of Internal Medicine》杂志中报导的二项研究显示,流行性感冒疫苗符合成本效益,但在成人却未被适当使用。这项研究发现,三大健康维持机构对老年患者在两个流行性感冒的季节,使用流行性感冒疫苗可以降低38%至50%死亡率。
  
  这一系列的研究是由明尼苏达州Minneapolis 市的退伍军人管理局的医学中心的Kristin Nichol医师及其同事进行,研究分析了1996-1997年间122,974人的资料与1997-1998年间158,454人的资料。在未接种的人中,第一年健康人因肺炎或流行性感冒而住院或死亡的比例是每1000人有8.2人,高危险群的比例是每1000人有38.4人,第二年在健康人的比例为每1000人有8.2人,高危险群的比例为每1000人有29.3人。
  
  经过调整,疫苗可以使住院或死亡的发生率在第一年降低48% (95%可信区间[CI], 42%-52%),第二年降低31%(95% CI,26%-37%),在高危险群中,绝对危险度的降低程度要比健康老年人的降低程度高2.4-4.7倍。老年人可以从疫苗接种获得实质上的好处,然而,流行性感冒对于高风险健康状态的人冲击最大。
  
  Dr. Poland建议,医师与医疗卫生体系应该承担责任,让老年人的流行性感冒疫苗接种达到高的覆盖率。尽管国家长期建议让流行性感冒免疫成为照护的标准,但提高流行性感冒疫苗覆盖率的进展,依然是非常地迟缓,虽经数十年的努力其覆盖率才达到60%。如果下个月出现一种同样安全有效的预防HIV感染的疫苗,我们会花几十年才将其提供给危险群中60%的人吗?
  
  Dr. Poland建议,应采取几种可能的策略,普遍让老年人接种流行性感冒的疫苗,这包括护士们对患者针对流行性感冒与肺炎双球菌疾病进行筛检与免疫的作战命令,提醒者与其它诊所办公系统,医疗保险与其它第三方支付人偿还疫苗及接种的费用,提供足够的疫苗库存,资助新疫苗的开发。对于下个全国的流行性感冒大流行,及利用生物工程流行性感冒作?群体毁灭的生物武器的可能性,我们必须设计且学会如何达到高的疫苗覆盖率。现在即是开始实施挽救数千条性命过程的时机。
  
  8月20日的《Annals of Internal Medicine》杂志上发表的一篇对流行性感冒疫苗接种的计算机化成本效益分析的结果,支持Dr. Poland的观点,并将其扩展到18-50岁的健康成年人。输入计算机模式的资料包括以前发表的流行性感冒疫苗接种及采用抗病毒药物治疗流行性感冒的成本与效益,因?疾病损失的工作时间,采用抗病毒药物的症状缓解时间。史丹佛大学的Patrick Lee医师及其同事,对210位在家庭医学科门诊的患者,就流行性感冒疫苗自付医药费用以达到缓解与无副作用的意愿进行调查。
  
  Dr. Lee指出,关于治疗措施的选择尚有许多争论,但研究显示,如果对所有人口进行免疫接种,并采用抗病毒药物对患者进行治疗的话,则社会整体而言是将获益。
  
  此模型预测策略包含疫苗接种在内,在1,000次类比中,有95%的可能可以达到最理想的成本效益,尽管不免疫接种在非常轻微的流行性感冒流行季节中,且发生流行性感冒的可能性低于6.3%时的结果较好。但85%的类比中,采用抗病毒药物进行流行性感冒的治疗效果很好,rimantidine与较新的药物zanamivir和oseltamivir同样有效。大多数流行性感冒流行的季节,整个社会进行免疫接种是有良好的成本效益,但若无足够的疫苗,则须先接种首需疫苗的人。
  
  
  
  

Flu Vaccine Cost-Effective But

By Laurie Barclay, MD
Medscape Medical News

Aug. 20, 2002 — The flu vaccine is cost-effective but underused in adults, according to authors of an editorial and study published in the Aug. 15 issue of Clinical Infectious Diseases and a second study in the Aug. 20 issue of the Annals of Internal Medicine.

"If you could halve the mortality rate, would you do it?" Gregory Poland, MD, from the Mayo Clinic, asks in his editorial, citing the accompanying CID study which found that influenza vaccination of elderly patients in three large health maintenance organizations over two flu seasons reduced the mortality rate by 38% to 50%.

That serial cohort study, by Kristin Nichol, MD, from the VA Medical Center in Minneapolis, Minnesota, and colleagues, analyzed data from 122,974 persons during the 1996-1997 season and from 158,454 persons during the 1997-1998 season. Among unvaccinated persons, hospitalizations for pneumonia or influenza or death occurred in 8.2 of 1,000 healthy and 38.4 of 1,000 high-risk persons in the first year, and in 8.2 of 1,000 healthy and 29.3 of 1,000 high-risk persons in the second year.

After adjustments, vaccination reduced the incidence of hospitalization or death by 48% (95% confidence interval [CI], 42%-52%) in the first year and by 31% (95% CI, 26%-37%) in the second year, with absolute risk reduction 2.4- to 4.7-fold higher among high-risk than among healthy elderly persons.

"All elderly individuals may substantially benefit from vaccination," the authors write. "However, the impact of influenza is greater in persons with high-risk medical conditions."

Poland recommends that physicians and health-care systems assume responsibility for achieving high influenza vaccine-coverage rates in the elderly. "Despite long-standing national recommendations that make influenza immunization the standard of care, progress in improving influenza coverage rates has been unacceptably slow at best, taking decades to achieve coverage rates of 60%," he says in a news release. "If an equally safe and effective vaccine to prevent HIV infection were available next month, would it take us decades to offer it to 60% of the at-risk population?"

He suggests several potential strategies to achieve universal influenza vaccination of the elderly, including standing orders for nurses to screen and immunize patients for influenza and pneumococcal disease, reminder and other clinic office systems, reimbursement by Medicare and other third-party payors for the cost of the vaccine and its administration, providing adequate stocks of available vaccine, and funding new vaccine development. "We must devise and learn how to achieve high influenza immunization rates for the eventuality of the next influenza pandemic and for the possibility of bioengineered influenza used as a bioweapon of mass destruction," Poland says. "Now is the time to get it right and begin the process of saving thousands of lives."

A computerized cost-benefit analysis of influenza vaccination, published in the Aug. 20 issue of the Annals of Internal Medicine, supports Poland's views and extends them to healthy adults aged 18 to 50 years. Data entered in the computer model included previously published data on the costs and benefits of flu vaccination and treatment of influenza with antiviral drugs, lost work time due to illness, and duration of symptom relief from antiviral drugs. Patrick Lee, MD, from Stanford University in California, and colleagues also surveyed 210 patients at a family practice clinic about their willingness to pay for flu symptom relief and medication without adverse effects.

"There's been a lot of debate about optimal treatment strategies," Lee says. "Our study shows that society as a whole benefits if you vaccinate the entire population and use antiviral medications on those who get sick."

The model predicted that a strategy including vaccination was optimally cost-beneficial in 95% of 1,000 runs, although nonvaccination gave better outcomes during very mild flu seasons when the probability of contracting flu was less than 6.3%. Treatment of influenza with antiviral medications was optimal in 85% of runs, and rimantidine was as effective as the newer drugs zanamivir and oseltamivir. "For most flu seasons, it is cost-beneficial for the whole society to be vaccinated," Lee says. "But if there's not enough vaccine to go around, you need to vaccinate those who need it most first."

Ann Intern Med. 2002;137:225-231
Clin Infect Dis. 2002;35(4): 370-377, 378-380

Reviewed by Gary D. Vogin, MD

    
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