Long-term follow-up of antibody titers after hepatitis A vaccination

Abstract To evaluate the potential long-term efficacy of hepatitis A vaccination for prevention of hepatitis A virus(HAV) infection, anti-HAV titers in serum were measured serially. Twelve anti-HAV-negative volunteers were injected with 0.25, 0.5 or 1.0, μg of hepatitis A vaccine at time zero, 1 and 6 months, and anti-HAV titers were monitored over a 54-month interval after the first injection. In addition, another 33 volunteers were injected with 0.5, μg of hepatitis A vaccine at time zero and 2 weeks, and anti-HAV titers were measured until 18 months. All the volunteers given two or three vaccinations seroconverted to anti-HAV by 1 month after the second injection. In subjects undergoing three injections, all remained anti-HAV positive during the observation period and the geometric mean titers (GMTs) were greater than 100 mIU/ml. In subjects undergoing two injections, anti-HAV remained positive until 18 months after the first vaccination. We therefore conclude that the hepatitis A vaccine induces a sustained anti-HAV antibody titer.