Emergency vaccination against epidemic meningitis in Ghana: Implications for the control of meningococcal disease in West Africa

Background. Recurrent epidemics of meningococcal disease have been reported throughout the African meningitis belt since description of the disease in 1912. Meningooccal polysaccharide vaccines can effectively prevent disease but the optimum strategy for their use in this setting has been controversial. We used data from an outbreak of meningococcal disease in northern Ghana in 1997 to assess the potential effect of different vaccination strategies. Methods. We identified all reported cases of meningococcal meningitis and estimated the number of cases and deaths that could have been prevented by vaccination through use of a simple mathematical model. We then assessed the potential effect of different vaccination strategies and the burden of these strategies on the public-health system. Findings. In the three affected regions in northern Ghana there were 18,703 cases and 1356 deaths reported between November, 1996, and May, 1997. Vaccination began in the third week of February and continued to April, reaching 72 of the at-risk population and preventing an estimated 23 of cases and 18 of deaths. A strategy of routine childhood and adult immunisation would have prevented 61 of cases had this same rate of vaccine coverage been achieved and maintained before the epidemic. If vaccination had started after the onset of the epidemic in January, as currently advocated by WHO guidelines, a similar proportion (61) of cases could have been prevented. Interpretation. Prevention of epidemics of meningococal disease in west Africa will be difficult until long-lasting conjugate vaccines capable of interrupting transmission of Neisseria meningitidis can be incorporated into routine infant-immunisation schedules. Until then, the strategy of surveillance and response advocated by WHO is as effective and more practical than a strategy of routine childhood and adult vaccination with currently available polysaccharide vaccines. This study assessed the potential effects of different vaccination strategies using data from the 1997 meningococcal outbreak in northern Ghana. Since the description of the disease in 1912, recurrent epidemics of meningococcal disease have been reported throughout the African meningitis belt. The use of meningococcal polysaccharide vaccines has been proven to effectively prevent the disease, although the method of vaccine distribution was disputable. Using a simple mathematical model, meningococcal meningitis cases and deaths, which could have been forestalled by vaccination, were identified, and the effect of developed vaccination strategies on the public health system was analyzed. About 18,703 cases and 1356 deaths were reported in 3 regions of northern Ghana between November 1996 and May 1997. Vaccination was conducted between February and April, which covered 72% of the high-risk population and prevented approximately 23% of cases and 18% of deaths. Routine childhood and adult immunization would have prevented 61% of cases had this same rate of vaccine coverage been achieved and maintained before the epidemic. This study suggests that the prevention of the meningococcal disease epidemic in West Africa would be difficult unless long-lasting conjugate vaccines are incorporated into routine infant immunization schedules. For now, the surveillance and response strategies advocated by the WHO serve as an effective and practical intervention.

Source: UG