A lot of elderly people travel to hepatitis A endemic areas. The prevalence of hepatitis A IgG positivity is declining in the Netherlands, also in the elderly. Studies show that people above 40 years of age have a slower immune response to hepatitis A vaccination. However, a lot of travelers seek pre-travel advice only shortly before their journey. More information about the time to adequate antibody response after hepatitis A vaccination is required to provide good protection during travelling. Alternative protection with immunoglobulins are available.

Study design: Observational, longitudinal pilot study Study population: 20 adults over 60 years of age with a negative hepatitis A IgG, (with a estimated 50% positivity for hepatitis A IgG in this age Group, 40 patients in this age group) 20 adults 18-40 years of age as controls.

Intervention (if applicable): When hepatitis A vaccination is indicated and informed consent is obtained, hepatitis A IgG wil be measured at day 0, 7, 14, 21 en 28.

Main study parameters/endpoints: Time to protective hepatitis A IgG. Nature and extent of the burden and risks associated with participation, benefit and group relatedness: hepatitis A vaccination will be given also outside this study. In the study 5 venous punctures of 7 ml of blood.

Exclusion Criteria:

• previous hep A vaccination
• known hepatitis A serology status
• immunodeficiency

80 >60 years, hepatitis A vaccination indicated 40 < 40 years, hepatitis A vaccination indicated