Hib Conjugate Vaccine Effective as Routine Immunization in the Gambia

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Hib Conjugate Vaccine Effective as Routine Immunization in the Gambia

Despite incomplete coverage and problems with supply, two doses of a Hib conjugate vaccine eliminated Hib disease in Gambian children.

Haemophilus influenzae type b (Hib) conjugate vaccines have been highly effective in developed countries. Because of high vaccine cost and lack of information on the burden of Hib disease, use has lagged in poor nations. In the Gambia, routine infant immunization with an Hib polysaccharide–tetanus toxoid conjugate vaccine (PRP-T) began in May 1997. Investigators have conducted surveillance for invasive Hib disease in western regions of that country (population, 836,000) to assess vaccine effectiveness in preventing invasive Hib infection and to estimate its indirect benefits in children.

From May 1997 through April 2002, the annual incidence of Hib meningitis per 100,000 children dropped from >200 to 0 in those aged <1 year and from 60 to 0 in those aged <5 years. Vaccine effectiveness against Hib meningitis was estimated to be 93% after two doses. Based on age distribution of meningitis cases recorded before and after routine PRP-T use, only 41% of the decrease in disease incidence was estimated to be due to direct vaccine effects. Positive oropharyngeal cultures for Hib in a sample of 1- to 2-year-olds dropped from 236 per 2000 children in 1992–1993 to 5 per 2000 in 2000–2001.

Comment: Two doses of PRP-T, delivered through routine immunization programs, provided excellent protection against invasive disease despite incomplete coverage and problems with vaccine supply. Much of the benefit appears to derive from indirect effects, probably through decreased Hib colonization. As noted by editorialists, the Global Alliance for Vaccines and Immunization may facilitate introduction of Hib vaccines into developing countries.

— Mary E. Wilson, MD

Published in Journal Watch Infectious Diseases August 5, 2005

Citation(s):

Adegbola RA et al. Elimination of Haemophilus influenzae type b (Hib) disease from The Gambia after the introduction of routine immunisation with a Hib conjugate vaccine: A prospective study. Lancet 2005 Jul 9; 366:144-50.

Medline abstract (Free)

Clemens J and Jodar L. Hib vaccines for all the world’s children? Lancet 2005 Jul 9; 366:101-3.

Medline abstract (Free)

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