Objectives: To assess risk factors for decreased immunogenicity among adults vaccinated with hepatitis B vaccine and to determine the importance of differences in immunogenicity between vaccines among health care workers (HCWs). Design: Randomized clinical trial and decision analysis. Participants: HCWs. Main Outcome Measures: Development of seroprotective levels of antibody to hepatitis B surface antigen (anti-HBs) and the number of expected chronic hepatitis B virus (HBV) infections associated with lack of protection. Results: Overall, 88% of HCWs developed seroprotection. Risk factors associated with failure to develop seroprotection included increasing age, obesity, smoking, and male gender (P < .05). Presence of a chronic disease was associated with lack of seroprotection only among persons greater than or equal to 40 years of age (P <.05). The two vaccines studied differed in their overall seroprotection rates (90% vs. 86%; P < .05), however, this difference was restricted to persons greater than or equal to 40 years of age (87% vs. 81%; P < .01). Among HCWs greater than or equal to 40 years of age, the decision anal)sis found 44 (0.34/100,000 person-years) excess chronic HBV infections over the working life of the cohort associated with use of the less immunogenic vaccine compared to the other. Conclusion: Hepatitis B vaccines are highly immunogenic, but have decreased immunogenicity associated with increasing age, obesity, smoking, and male gender; and among older adults, the presence of a chronic disease. One of the two available vaccines is more immunogenic among older adults; however, this finding has little clinical or public health importance. Hepatitis B vaccines should be administered to persons at occupational risk for HBV infection early in their career, preferably while they are still in their training.
