An open study of subcutaneous administration of inactivated hepatitis A vaccine (VAQTA((R))) in adults: safety, tolerability, and immunogenicity

A number of patients in clinical practice would be candidates for hepatitis A vaccine administered subcutaneously (SC), including patients with inheri ted and acquired coagulopathies. To assess the safety, tolerability, and im munogenicity of VAQTA((R)) (Hepatitis A Vaccine, Inactivated, Merck and Co. Inc., West Point, PA) was administered SC to healthy adults. A total of 11 4 healthy adults received two doses of vaccine SC 24 weeks apart. No seriou s vaccine-related adverse experiences were reported. Four weeks after dose 1, the seropositivity rate (SPR) was 77.9% (CI, 69.1, 85.1%). The geometric mean titer. (GMT) was 21.0 mIU/ml. Twenty-four weeks after dose 1 (just pr ior to dose 2) and 28 weeks after dose I(four weeks following dose 2), the SPR were 95.3 and 100%, respectively; the GMTs were 153.2 and 1563.9 mIU/ml , respectively. Although the kinetics of the immune response were slower wh en VAQTA((R)) was administered SC compared to intramuscular injection, SPRs and GMTs increased over time, indicating that the vaccine administered SC demonstrated immunogenicity. (C) 2001 Elsevier Science Ltd. All rights rese rved.