Simultaneous vaccination against hepatitis A and B: results of an open, randomized study from the occupational health point of view.

Objectives: The primary objective of the study was to evaluate the immunogenicity of a combined hepatitis A and hepatitis B vaccine compared to the effect of the administration of two monovalent hepatitis A and B vaccines by quantitative measurements of the anti-HBs antibody levels at month 2 of the vaccination course. Secondary objectives were to assess immunogenicity of the vaccines investigated at other time points in the vaccination course (months 1, 6 and 7), including the comparison of quantitative measurements results as well as to evaluate seroconversion and seroprotection rates.

Materials And Methods: The study was designed as open, controlled, randomized, monocentric study with two parallel groups. A total of 304 subjects, aged 18-45 years, were enrolled in the study. Group 1 received a combined hepatitis A and hepatitis B vaccine, group 2 was vaccinated concomitantly with a monovalent hepatitis A and hepatitis B vaccine. Seroprotection against hepatitis B was defined as anti-HBs antibody concentration > or =10 IU/l, and longterm seroprotection as > or =100 IU/l.

Results: In all, 288 subjects completed the study. One month after the second vaccine dose, the percentage of subjects with anti-HBs antibody concentrations > or =100 IU/l as well as the seroconversion rate were significantly higher in group 1 than in group 2. Similarly, anti-HBs GMC was higher after combined vaccination one month after the third vaccine dose (1.684 IU/l vs. 528 IU/l; p < 0,0001). After the vaccination course, all individuals were anti-HAV positive. The overall incidence of symptoms (solicited/unsolicited, local/general) tended to be similar in each of the two groups.

Conclusions: If health care personnel are exposed to hepatitis A and B virus, the combined vaccination should be preferred to the concomitant one, as this vaccination scheme induced earlier seroprotection against hepatitis B virus infection (> or =10 IU/l and > or =100 IU/l).