Impact of conjugate Haemophilus influenzae type b (Hib) vaccine introduction in South Africa

Objective To analyse trends in reported invasive Haemophilus influenzae disease in South Africa within the first five years of introduction of conjugate Haemophilus influenzae type b (Hib) vaccine in the routine child immunization schedule. Methods We used national laboratory-based surveillance data to identify cases of invasive H. influenzae disease between July 1999 and June 2004, and submitted isolates for serotyping and antimicrobial susceptibility testing. Findings The absolute number of Hib cases (reported to the national surveillance system) among children below one year of age decreased by 65%, from 55 cases in 1999-2000 to 19 cases in 2003-04. Enhanced surveillance initiated in 2003, identified human immunodeficiency virus (HIV)-infection and incomplete vaccination as contributing factors for Hib transmission. The total number of laboratory-confirmed cases of H. influenzae remained unchanged because non-type b disease was being increasingly reported to the surveillance system concomitant with system enhancements. Children with non-typable disease were more likely to be HIV-positive (32 of 34, 94%) than children with Hib disease (10 of 14, 71%), P = 0.051. Recent Hib isolates were more likely to be multidrug resistant (2% in 1999-2000 versus 19% in 2003-04, P = 0.001). Conclusion Data from a newly established national laboratory-based surveillance system showed a decrease in Hib disease burden among South African children following conjugate vaccine introduction and identified cases of non-typable disease associated with HIV infection.