Abstract

A controlled trial with pre-exposure immune serum globulin was undertaken in Israel Defence Forces (IDF) recruits, an indigenous population living in a hyperendemic area for hepatitis A. The objective was to examine whether the prevailing IDF policy of postexposure administration of immune serum globulin prophylaxis should be modified to further reduce the incidence of infectious hepatitis in the IDF. Altogether 23 447 recruits were systematically allocated on their first day of service into an intervention group and a control group. Over the 18-month follow-up period 18 cases of non-B viral hepatitis were identified among the 10 943 vaccinees and 41 among the 12 504 non-immunised group. Protection over six months was about 85%, and over the entire 18 months 50%. Protection was evident until about 40 weeks' follow-up and may have persisted for longer. Rates in the non-immunised were lower than expected, alluding to the possibility of herd immunity. IDF immunisation policy was successfully altered after this trial.