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Fourteen years after the first introduction of conjugate Haemophilus influenzae type b vaccine in The Gambia, effective disease control was maintained, with associated low carriage and high seroprotection. Continued surveillance must determine if protection wanes and a booster dose is needed.Background. The Gambia was the first country in Africa to introduce conjugate Haemophilus influenzae type b (Hib) vaccine, which, as in other developing countries but unlike industrialized countries, is delivered as a 3-dose primary series with no booster. This study assessed its effectiveness 14 years after introduction.Methods. Using methods standardized during >20 years in the study site, clinical and microbiological surveillance for invasive Hib disease (primarily meningitis) in the Western Region of The Gambia from 2007 to 2010 was complemented with studies of Hib carriage in children aged 1 to <2 years, Hib antibody levels in children aged <5 years, and Hib vaccine coverage and timing in children aged 1 to <2 years.Results. The incidence of Hib meningitis remained low (averaging 1.3 per 100 000 children aged <5 years annually), as did the Hib oropharyngeal carriage rate (0.9%). Hib antibody levels were protective in >99% of those surveyed, albeit with lower titers in older children; and coverage of conjugate Hib vaccination was high (91% having 3 doses at 1–2 years of age) using a schedule that was delivered at median ages of 2.6 months, 4.3 months, and 6 months for the first, second, and third doses, respectively.Conclusions. Conjugate Hib vaccine was delivered on time in a 3-dose primary series without booster to a high proportion of eligible children and this was associated with effective disease control up to 14 years after introduction. It is important that surveillance continues in this first African country to introduce the vaccine to determine if effective control persists or if a booster dose becomes necessary as has been the case in industrialized countries. [ABSTRACT FROM AUTHOR]

Abstract: Invasive Hib disease, which remains a major cause of childhood mortality and morbidity in most of the developing world, was eliminated in The Gambia by 2002 following the introduction of conjugate Hib vaccine in 1997. Formal disease surveillance was stopped in 2002 but five cases (including three of meningitis) were detected non-systematically between July 2005 and April 2006. This equates to an incidence of 3 per 100,000 annually for meningitis, a likely underestimate. The age distribution of cases (median 15 months, range 0–36 months) was older than previously seen and there were examples of apparent vaccine failure, but the cause for this re-emergence is not clear. No evidence was found of the emergence of a hypervirulent strain. The re-establishment of continuing surveillance is required to answer the questions raised by this report, and is particularly important in settings like The Gambia, where a booster dose is not given, to determine long-term effects of national immunisation with Hib vaccine. [Copyright &y& Elsevier]