The Immunogenicity of a Single Dose of Hepatitis A Virus Vaccines (Havrix® and Epaxal®) in Korean Young Adults

PURPOSE: Assessing the immunogenicity of a single dose of hepatitis A virus (HAV) vaccines is important because some people receive only a single dose. However, previous studies have shown variable results and have not examined the effects of demographic characteristics other than gender. This study was performed to examine the immunogenicity of a single dose of HAV vaccine according to the vaccine type and demographic characteristics in young adults. MATERIALS AND METHODS: Seronegative medical school students were randomly allocated to receive either Havrix or Epaxal. RESULTS: After approximately 11 months, the seroconversion rate in 451 participants was 80.7%. In men, the Havrix group showed a significantly higher seroconversion rate (81.9%) than the Epaxal group (69.2%), whereas both vaccine groups showed similarly high immunogenicity in women (Havrix: 90.1%, Epaxal: 92.9%; P for interaction=0.062). According to the results of a multivariate analysis, Epaxal showed significantly lower immunogenicity than Havrix only in men. Age, obesity, drinking, smoking, and follow-up time did not significantly affect seroconversion in either gender. CONCLUSION: The seroconversion rate of single-dose HAV vaccines was low in men, particularly in those who received Epaxal. Our results suggest that gender effects should be considered when comparing the immunogenicity of different HAV vaccines.