Control of hepatitis A by inactivated vaccines: unanswered questions and unresolved issues.

The recent development of safe and effective inactivated hepatitis A virus vaccines provides for the first time the opportunity to control hepatitis A. However, control will depend upon the intelligent use of the vaccines. How and when hepatitis A vaccines should be used will be determined from the results of studies of the levels and duration of protective antibody, determination of optimum immunization schedules, estimations of the continuing need for normal immune globulin and discussions of how hepatitis A vaccine can be incorporated into national and international vaccination programs. Cost and feasibility will determine whether live attenuated hepatitis A vaccines will become useful adjuncts or replacements for inactivated hepatitis A vaccines.