肥胖會影響流感疫苗的反應


  【24drs.com】根據線上國際肥胖期刊(International Journal of Obesity)上的一篇研究結論,隨著流感季節開始,北卡羅來納大學教堂山分校的研究者首次提出,流感疫苗對肥胖者的保護力可能小於健康體重者。
  
  一項針對學院門診中心接種疫苗患者所進行的研究,前兩年的結果指出,身體質量指數(BMI)較高與接種疫苗後12個月流感抗體降低較多有關;之前的研究認為肥胖與感染流感風險有關,但是這是首度有研究者檢測接種疫苗後的抗體。
  
  北卡羅來納大學教堂山分校Gillings全球公衛學院營養系的Patricia Sheridan博士等人藉由接種疫苗後的血清檢測發現,對三價流感疫苗而言,體重對於剛接種後反應的影響不大,不過,12個月後檢測CD8+ T細胞反應時發現,肥胖程度提高時,流感抗體降低達4倍,CD8+ T細胞不足以預防感染流感,但還是有助於減輕嚴重性和加速病毒清除。
  
  北卡羅來納大學教堂山分校Gillings全球公衛學院營養系副主任Melinda Beck教授在聲明中表示,這些結果認為,過重和肥胖者比健康體重者更可能被流感病毒感染,這些新結果似乎讓我們有理由瞭解為何在H1N1大流行時,肥胖者比健康體重者更容易發病。
  
  研究人員在2009年流感季檢測了461名18歲以上的成人病患、在2010年檢測了74人;這些病患29.7%是健康體重(BMI,18.5 - 24.9 kg/m2)、33.4%是過重(BMI,25 - 29.9 kg/m2)、35.5%是肥胖(BMI,≧30 kg/m2),其他1.4%體重過輕。
  
  接種疫苗12個月後,50%的肥胖病患顯示對兩種流感病毒株的抗體效價降低至少4倍,相較之下,健康體重者不到25%出現這種程度的抗體效價降低。
  
  肥胖也會降低成人對B型肝炎疫苗、孩童對破傷風疫苗的抗體反應。
  
  根據世界衛生組織統計,全球的肥胖人口超過10%,美國人口超過三分之一是過重或肥胖。
  
  資料來源:http://www.24drs.com/professional/list/content.asp?x_logon=W&x_idno=6638&x_classno=0
  

Obesity Affects Influenza Vaccine Response

By Larry Hand
Medscape Medical News

October 25, 2011 — As the influenza season opens this month, researchers at the University of North Carolina at Chapel Hill warn for the first time that obese individuals may be getting less protection from vaccines than healthy-weight people. They reported their conclusions in an article published online October 25 in the International Journal of Obesity.

In an ongoing study involving patients getting vaccinated at an academic outpatient center, results from the first 2 years indicate that higher body mass index (BMI) is associated with a larger drop in influenza antibodies 12 months after vaccination with trivalent influenza vaccine. Previous research had linked obesity to risk for influenza infection, but this is the first time researchers have tested for antibodies a year after vaccination.

Using serum tests just after vaccination, Patricia Sheridan, PhD, from the Department of Nutrition, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, and colleagues found that weight did not make a significant difference in the initial response to trivalent influenza vaccine. However, in testing for CD8+ T-cell responses to vaccines 12 months later, the researchers discovered that as obesity levels increased, influenza antibodies decreased up to 4-fold. The CD8+ T-cells do not prevent infection by influenza, but they do help decrease severity and speed up viral clearance.

"These results suggest that overweight and obese people would be more likely than healthy weight people to experience flu illness following exposure to the flu virus," Melinda Beck, PhD, professor and associate chair of nutrition at the University of North Carolina Gillings School of Global Public Health and senior author, said in a statement. "These new findings seem to give us a reason why obese people were more susceptible to influenza illness during the H1N1 pandemic compared to healthy weight people."

Researchers tested 461 adult patients aged 18 years or older during the 2009 influenza season, as well as 74 patients for the 2010 season. Of all the participants, 29.7% were healthy-weight individuals (BMI, 18.5 - 24.9 kg/m2), 33.4% were overweight (BMI, 25 - 29.9 kg/m2), and 35.5% were obese (BMI, ?30 kg/m2). The remaining 1.4% were underweight.

Twelve months after vaccination, 50% of the obese patients showed at least a 4-fold decrease in antibody titers to 2 influenza strains. In comparison, less than 25% of the healthy-weight patients experienced similar large decreases in antibody titers.

Obesity also has been shown to reduce antibody response to hepatitis B vaccine in adults, and tetanus vaccine in children.

According to the World Health Organization, more than 10% of the world population is obese, and more than two thirds of the US population is overweight or obese.

Int J Obes. Published online October 25, 2011.

    
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