- Background and methods. An ongoing nationwide prospective surveillance study was initiated in Israel in October, 1988, to document childhood invasive infections caused by Haemophilus influenzae type b (Hib), Streptococcus pneumoniae and Neisseria meningitidis. This study enabled us to document the effect on childhood invasive Hib disease of the introduction of conjugate Hib vaccines to Israel. Results. The incidence of invasive Hib disease before the age of 5 years dropped from 34 per 100 000 before initiation of immunization to < 5 per 100 000 in 1995 and is projected to be <4 in 1996. After <2 years, when various conjugate vaccines had been available in the private sector alone and had achieved partial coverage only, the Israeli Ministry of Health decided to add Hib conjugate vaccine to the regular infant immunization program, free of charge, effective for all infants born after January 1, 1994. The vaccine chosen was Hib polysaccharide linked to outer membrane protein complex of N. meningitidis B. Vaccine coverage has exceeded 90% of all infants born since January 1, 1994. Efficacy and effectiveness during the first 34 months of the program (January 1, 1994, to October 31, 1996) were 95.4 and 99.7%, respectively, for all invasive Hib disease and 97 and 99.4%, respectively, for Hib meningitis. Conclusion. The described ongoing surveillance program showed the existence and extent of Hib problems in Israel and documented the success of the immunization program in essentially eliminating the disease in Israel.