An open study of inactivated hepatitis A vaccine (VAQTA) in Taiwanese healthy adult volunteers: safety, tolerability, and immunogenicity.

The safety, tolerability and immunogenicity of inactivated hepatitis A vaccine (VAQTA, Merck and Co. Inc., West Point, PA, USA) were investigated in 28 seronegative healthy adult volunteers. The age range was 25-35 years, and the mean age was 29 years. Two doses of the vaccine, each containing 50 U of hepatitis A virus antigen, were administered into the deltoid region 24 weeks apart. No serious vaccine-related adverse reactions were reported. Four weeks after the first dose, the geometric mean titer (GMT) was 150 mIU/mL, and the seroconversion rate was 100%. Twenty eight weeks after the first dose (4 weeks following the second dose), the GMT was 4576 mIU/mL. This study demonstrated that VAQTA is safe and highly immunogenic in healthy young adults in Taiwan.