Vaccination against hepatitis A: a review of the evidence

The vaccine against hepatitis A is very highly immunogenic. Its excellent efficacy in pre-exposure prophylaxis has been documented extensively. Vaccination has proven to be effective in controlling outbreaks and preventing cases due to secondary exposure. Active immunization has shortened the course of outbreaks when coverage has reached approximately 80% in a well-defined target population. No clinical trial is yet available on the effectiveness during outbreaks of vaccination compared to the administration of normal human immunoglobulins. Although used in the past for post-exposure prophylaxis, immunoglobulin preparations have decreased antibody titers, but they are difficult to obtain and are not well accepted due to their human origin. Only one clinical vaccine trial for post-exposure prevention of disease has shown good efficacy (about 80%). However, confidence intervals are wide, and it is very difficult to obtain a sufficient number of study patients. In communities with recurrent epidemics or outbreaks, the use of vaccination is justified by the high secondary attack rates and the resulting acceptable cost-effectiveness. However, implementing routine vaccination programs for children and/or adolescents seems the most reasonable way to control recurrent outbreaks in areas where hepatitis A is a public health problem.