Background: Early field trial of the hepatitis B vaccine reported a poor response in 5∼15% of recipients. Hemodialysis, immunosuppression, age, smoking and obesity have been reported to be associated with poor anti-HBs response. There were scant data on the relationship between obesity and anti-HBs response. We conducted this survey to assess obesity as a risk factor of poor response to hepatitis B vaccine.
Method: Study participants included 204 obese adults who visited obesity clinic and 102 adults with normal weight who visited department of family medicine in a general hospital. Information on hepatitis B vaccine, smoking, alcohol drinking was obtained by a self-questionnaire. Body mass index (BMI) was assessed and anti-HBs was measured by radioimmunoassasy (RIA). We analyzed the associated factors for poor response of hepatitis B vaccine by multiple logistic regression analysis.
Results: The proportion of age under 40 years, obesity, and smoking were significantly higher in anti HBs(-) group than anti HBs(+) group. The odds ratio for anti HBs(-) in obesity group was 2.25 (95% CI: 1.11∼4.58) and that in smoker was 2.22 (95% CI: 1.02∼4.82). There was no significant association between age, sex, or alcohol drinking and anti HBs(-) by multiple logistic regression analysis.
Conclusion: Obesity and smoking have been recognized as related factors of poor response to hepatitis B vaccine. Vaccine dose, injection site, and length of needle have to be considered for acquisition of anti HBs to hepatitis B vaccine in obese subjects. Further study is needed to investigate the effect of quitting smoking and weight control to improve response of hepatitis B vaccine.

Keywords: obesity, Hepatitis B vaccine, Anti HBs, Response