Prevention of viral hepatitis A: past, present and future.

Before hepatitis A virus (HAV) was identified, spread of hepatitis A was prevented by public health measures. The first specific, preventive measure for hepatitis A was passive protection with standard, pooled human immune globulins. Human immune globulin contained sufficient HAV neutralizing antibodies for short-term, prophylactic passive protection and for control of the spread of local outbreaks. After many unsuccessful attempts, HAV was propagated in cell cultures and the development of vaccines for active immunization began. Formalin-inactivated, whole HAV induced protective immunity, and such formalin-inactivated hepatitis A vaccines are now being evaluated in large-scale clinical trials. HAV attenuated by serial propagation in cell culture has been used for several, live, attenuated hepatitis A vaccines and results of clinical trials are reassuring. Future approaches to protection against hepatitis A are likely to include vaccination with: hybrid viruses; hepatitis A antigen-expressing, genetically-engineered bacteria; purified hepatitis A antigens produced by molecular biological techniques and incorporated into slow or pulse-releasing systems; synthetic peptides or idiotypes.