流行性感冒疫苗符合成本效益,但在成人未被適當使用


  8月15日的《Clinical Infectious Disease》雜誌與8月20日的《Annals of Internal Medicine》雜誌中報導的二項研究顯示,流行性感冒疫苗符合成本效益,但在成人卻未被適當使用。這項研究發現,三大健康維持機構對老年患者在兩個流行性感冒的季節,使用流行性感冒疫苗可以降低38%至50%死亡率。
  
  這一系列的研究是由明尼蘇達州Minneapolis 市的退伍軍人管理局的醫學中心的Kristin Nichol醫師及其同事進行,研究分析了1996-1997年間122,974人的資料與1997-1998年間158,454人的資料。在未接種的人中,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,高危險群的比例是每1000人有38.4人,第二年在健康人的比例為每1000人有8.2人,高危險群的比例為每1000人有29.3人。
  
  經過調整,疫苗可以使住院或死亡的發生率在第一年降低48% (95%可信區間[CI], 42%-52%),第二年降低31%(95% CI,26%-37%),在高危險群中,絕對危險度的降低程度要比健康老年人的降低程度高2.4-4.7倍。老年人可以從疫苗接種獲得實質上的好處,然而,流行性感冒對於高風險健康狀態的人衝擊最大。
  
  Dr. Poland建議,醫師與醫療衛生體系應該承擔責任,讓老年人的流行性感冒疫苗接種達到高的覆蓋率。儘管國家長期建議讓流行性感冒免疫成為照護的標準,但提高流行性感冒疫苗覆蓋率的進展,依然是非常地遲緩,雖經數十年的努力其覆蓋率才達到60%。如果下個月出現一種同樣安全有效的預防HIV感染的疫苗,我們會花幾十年才將其提供給危險群中60%的人嗎?
  
  Dr. Poland建議,應採取幾種可能的策略,普遍讓老年人接種流行性感冒的疫苗,這包括護士們對患者針對流行性感冒與肺炎雙球菌疾病進行篩檢與免疫的作戰命令,提醒者與其他診所辦公系統,醫療保險與其他第三方支付人償還疫苗及接種的費用,提供足夠的疫苗庫存,資助新疫苗的開發。對於下個全國的流行性感冒大流行,及利用生物工程流行性感冒作?群體毀滅的生物武器的可能性,我們必須設計且學會如何達到高的疫苗覆蓋率。現在即是開始實施挽救數千條性命過程的時機。
  
  8月20日的《Annals of Internal Medicine》雜誌上發表的一篇對流行性感冒疫苗接種的電腦化成本效益分析的結果,支持Dr. Poland的觀點,並將其擴展到18-50歲的健康成年人。輸入電腦模式的資料包括以前發表的流行性感冒疫苗接種及採用抗病毒藥物治療流行性感冒的成本與效益,因?疾病損失的工作時間,採用抗病毒藥物的症狀緩解時間。史丹佛大學的Patrick Lee醫師及其同事,對210位在家庭醫學科門診的患者,就流行性感冒疫苗自付醫藥費用以達到緩解與無副作用的意願進行調查。
  
  Dr. Lee指出,關於治療措施的選擇尚有許多爭論,但研究顯示,如果對所有人口進行免疫接種,並採用抗病毒藥物對患者進行治療的話,則社會整體而言是將獲益。
  
  此模型預測策略包含疫苗接種在內,在1,000次類比中,有95%的可能可以達到最理想的成本效益,儘管不免疫接種在非常輕微的流行性感冒流行季節中,且發生流行性感冒的可能性低於6.3%時的結果較好。但85%的類比中,採用抗病毒藥物進行流行性感冒的治療效果很好,rimantidine與較新的藥物zanamivir和oseltamivir同樣有效。大多數流行性感冒流行的季節,整個社會進行免疫接種是有良好的成本效益,但若無足夠的疫苗,則須先接種首需疫苗的人。
  
  
  
  

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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