肺炎鏈球菌疫苗與嚴重肺併發症增加有關


  【24drs.com】January 13, 2010 — 根據一項發表於2010年1月號兒科醫學期刊的文章,七價肺炎鏈球菌接合疫苗(PCV7),成功地保護兒童免於肺炎鏈球菌感染,但也與因肺膿瘍住院機率上升有關。
  
  來自沙加緬度加州戴維斯大學兒科的Su-Ting Li醫師與Daniel Tancredi博士寫到,雖然PCV7可以顯著降低侵襲性肺炎雙球菌疾病的發生率,其對於肺膿瘍發生率的效應仍然未知。引進PCV7後進行的肺膿瘍發生率研究顯示不一致的結果:據報導,肺膿瘍發生率在猶他州增加了88%,在加州增加了400%,但在德州卻下降了55%,在加拿大魁北克則是沒有變化。
  
  在美國,肺炎是導致兒童住院的頭號原因;而肺炎鏈球菌又是細菌性肺炎(17-%28%)與肺膿瘍最常見的病原菌,造成肺部化膿。肺膿瘍與3%因為肺炎住院以及高達三分之一肺炎鏈球菌肺炎住院有關。美國於2000年2月發給PCV7使用執照。
  
  【研究發現肺膿瘍住院率增加了70%】
  為了確認與整個國家進行PCV7接種是否增加肺膿瘍發生率,研究者們使用兒童住院資料庫來估計1997年、2000年、2003年與2006年因為肺膿瘍住院的數據。這些估計值使用美國官方流行病學資訊,以每10萬位兒童年度發生率做圖。
  
  在比較這些時段的肺膿瘍發生率後,大約有2,898位年齡小於18歲的兒童(95%信賴區間[CI]為2532-3264)在2006年因為肺膿瘍住院,換算為住院率為每10萬名3.7位(95% CI為3.3-4.2)。這代表相較於1997年的每10萬名2.2位(95% CI為1.9-2.5),發生率上升了將近70%。所有肺炎併發症,包括肺膿瘍、肋膜積水或是需要植入胸管或進行外科手術的機率增加到每10萬名5.5位,換算起來增加了44%。
  
  即使細菌性肺炎機率下降13%,到每10萬名244.3位(95% CI為231.1-257.5),以及侵襲性肺炎鏈球菌疾病機率下降50%,到每10萬名6.3位(95% CI為5.7-6.9),這些變化仍然不變。
  
  作者們假定這些結果可能可以以該疫苗沒有特定肺炎鏈球菌血清型來解釋。舉例來說,PCV7包括4種血清型,分別為4、6B、9V、14、18C、19F與23F,但是未包括1,雖然這個血清型僅占細菌性肺炎的4%~7%,但卻是肺膿瘍的主要病因(24%~50%)。作者們也附帶表示,金黃色葡萄球菌造成的肺膿瘍可能增加,因為對methicillin具抗藥性的金黃色葡萄球菌越來越常見。
  
  【作者:雖然新疫苗在研發中,仍應繼續接種】
  雖然有這些研究發現,作者們仍然偏向繼續接種。
  
  Tancredi醫師在一篇新聞稿中表示,傾向造成肺膿瘍的肺炎比例仍然偏低,因此接種疫苗所帶來的好處仍然是非常大的。
  
  這項研究的限制包括資料分類錯誤的可能性,肋膜積水可能被錯誤編碼為肺膿瘍。而最近介入性治療的比例增加,也可能導致複雜性肺炎發生率增加的誤差。最後,研究作者表示細菌感染診斷是根據編碼,而罹患肺炎兒童的微生物學編碼目前尚未被確效。
  
  包括更多血清型的疫苗目前正在研發中。該廣泛型接合性疫苗是一種10價疫苗,包括血清型1、5、7F,而13價疫苗包括1、3、5、6A、7F與19A。根據作者們表示,一旦其他疫苗開始使用,進一步的研究將會是更適當的。
  
  Li醫師在新聞稿中表示,一旦新疫苗獲得核准上市、取得執照,且開始讓人們使用,我們會再次收集數據,屆時我們將會看到肺膿瘍發生率下降。
  
  加州戴維斯大學兒童醫學部門贊助這項研究。作者們表示已無相關資金上的往來。

Pneumococcal Vaccine Linked to Increase in Serious Lung Complication

By Nancy Fowler Larson
Medscape Medical News

January 13, 2010 — The heptavalent pneumococcal conjugate vaccine (PCV7), which successfully protects children from Streptococcus pneumoniae, is also associated with an increase in hospitalizations for empyema, according to an article published in the January issue of Pediatrics.

"Although PCV7 clearly reduced the incidence of [invasive pneumococcal disease], its effect on empyema incidence was less clear," write Su-Ting Li, MD, MPH, and Daniel Tancredi, PhD, from the Department of Pediatrics, University of California–Davis, Sacramento. "Studies of empyema incidence conducted after the introduction of PCV7 showed contradictory results: Empyema incidence was reported to have increased by 88% in Utah and by 400% in California but was shown to have decreased by 55% in Texas and remained unchanged in Quebec, Canada."

Pneumonia is the number one reason for pediatric hospitalization in the United States. Streptococcus pneumoniae is the most common cause of bacterial pneumonia (17% - 28%) and empyema, which causes pockets of purulence around the lungs. Empyema is linked to 3% of all pneumonia hospitalizations and up to one third of pneumococcal pneumonia hospitalizations. The United States licensed PCV7 in February 2000.

Study Finds 70% Increase in Empyema Hospitalizations

To determine whether the rise in empyema associated with PCV7 was present on a national level, researchers used figures from the Kids' Inpatient Database to estimate the number of pediatric patients hospitalized with empyema in 1997, 2000, 2003, and 2006. These estimates were figured as annual incidence rates per 100,000 children using US Census information.

After comparing these rates for the time periods studied, researchers found that approximately 2898 children younger than 18 years (95% confidence interval [CI], 2532 - 3264) were hospitalized with empyema in 2006 — a calculated hospitalization rate of 3.7 per 100,000 (95% CI, 3.3 - 4.2). That demonstrates a nearly 70% increase over the 1997 rate of 2.2 per 100,000 (95% CI, 1.9 - 2.5). A 44% increase, to 5.5 per 100,000 (95% CI, 4.8 - 6.1), was seen in the rate of all pneumonia complications including empyema, pleural effusion, or bacterial pneumonia that necessitated a chest tube or decortications.

These changes occurred even as the bacterial pneumonia rate declined 13%, to 244.3 per 100,000 (95% CI, 231.1 - 257.5), and the invasive pneumococcal disease rate decreased 50%, to 6.3 per 100,000 (95% CI: 5.7 - 6.9).

The authors posited that the results might be explained by the absence of certain pneumococcal serotypes from the vaccine. For example, PCV7 includes serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F, but not 1, which, although responsible for only 4% to 7% of bacterial pneumonia, is the chief cause of empyema (24% - 50%). The authors also added that empyemas caused by staphylococcus may be on the increase because of the rise of methicillin-resistant Staphylococcus aureus.

Continue Innoculations, Authors Say, While New Vaccine Is Developed

Despite their findings, the authors are still in favor of vaccination.

"[T]he fraction of pneumonia that tends to result in empyema is still low, so there is a huge benefit from immunization," Dr. Tancredi said in a press release.

Limitations of the study include the possibility of a data misclassification, in which pleural effusions may have been incorrectly coded as empyema. The authors also stated that a recent increase in intervention might have led to a bias toward a rise in complicated pneumonias. Finally, they noted that bacterial diagnosis is dependent on coding, and microbiology coding for children with pneumonia has not been validated.

A more inclusive vaccine is currently under development. This expanded-valency conjugate vaccine contains a 10-valent vaccine containing serotypes 1, 5, and 7F and a 13-valent vaccine that includes 1, 3, 5, 6A, 7F, and 19A. According to the authors, further studies will be appropriate once the alternate vaccine is in use.

"We're hoping that once the new vaccine is approved and licensed and distributed to patients we would look at the data again and that we would find decrease in the incidence of empyema," Dr. Li said in the press release.

The Department of Pediatrics at the University of California–Davis supported this study. The authors have disclosed no relevant financial relationships.

Pediatrics. 2010;125:26-33.

    
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