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Streptococcus pneumoniae is increasingly recognised as an important cause of bacterial meningitis in the African meningitis belt. The World Health Organization sets guidelines for response to outbreaks of meningococcal meningitis, but there are no current guidelines for outbreaks where S. pneumoniae is implicated. We aimed to evaluate the impact of using a similar response to target outbreaks of vaccine-preventable pneumococcal meningitis in the meningitis belt. Here, we adapt a previous model of reactive vaccination for meningococcal outbreaks to estimate the potential impact of reactive vaccination in a recent pneumococcal meningitis outbreak in the Brong-Ahafo region of central Ghana using weekly line list data on all suspected cases over a period of five months. We determine the sensitivity and specificity of various epidemic thresholds and model the cases and deaths averted by reactive vaccination. An epidemic threshold of 10 suspected cases per 100,000 population per week performed the best, predicting large outbreaks with 100% sensitivity and more than 85% specificity. In this outbreak, reactive vaccination would have prevented a lower number of cases per individual vaccinated (approximately 15,300 doses per case averted) than previously estimated for meningococcal outbreaks. Since the burden of death and disability from pneumococcal meningitis is higher than that from meningococcal meningitis, there may still be merit in considering reactive vaccination for outbreaks of pneumococcal meningitis. More outbreak data are needed to refine our model estimates. Whatever policy is followed, we emphasize the importance of timely laboratory confirmation of suspected cases to enable appropriate decisions about outbreak response.

Summary Background In preparation for the introduction of MenAfriVac, a meningococcal group A conjugate vaccine developed for the African meningitis belt, an enhanced meningitis surveillance network was established. We analysed surveillance data on suspected and confirmed cases of meningitis to quantify vaccine impact. Methods We compiled and analysed surveillance data for nine countries in the meningitis belt (Benin, Burkina Faso, Chad, Cote d'Ivoire, Ghana, Mali, Niger, Nigeria, and Togo) collected and curated by the WHO Inter-country Support Team between 2005 and 2015. The incidence rate ratios (IRRs) of suspected and confirmed cases in vaccinated and unvaccinated populations were estimated with negative binomial regression models. The relative risk of districts reaching the epidemic threshold of ten per 100 000 per week was estimated according to district vaccination status. Findings The incidence of suspected meningitis cases declined by 57% (95% CI 55–59) in vaccinated compared with unvaccinated populations, with some heterogeneity observed by country. We observed a similar 59% decline in the risk of a district reaching the epidemic threshold. In fully vaccinated populations, the incidence of confirmed group A disease was reduced by more than 99%. The IRR for non-A serogroups was higher after completion of MenAfriVac campaigns (IRR 2·76, 95% CI 1·21–6·30). Interpretation MenAfriVac introduction has led to substantial reductions in the incidence of suspected meningitis and epidemic risk, and a substantial effect on confirmed group A meningococcal meningitis. It is important to continue strengthening surveillance to monitor vaccine performance and remain vigilant against threats from other meningococcal serogroups and other pathogens. Funding World Health Organization.

OBJECTIVE: To investigate potential risk factors for acquisition in seven countries of the meningitis belt. METHODS: Households were followed up every 2 weeks for 2 months, then monthly for a further 4 months. Pharyngeal swabs were collected from all available household members at each visit and questionnaires completed. Risks of acquisition over the whole study period and for each visit were analysed by a series of logistic regressions. RESULTS: Over the course of the study, acquisition was higher in: (i) 5-to 14-year olds, as compared with those 30 years or older (OR 3.6, 95% CI 1.4-9.9); (ii) smokers (OR 3.6, 95% CI 0.98-13); and (iii) those exposed to wood smoke at home (OR 2.6 95% CI 1.3-5.6). The risk of acquisition from one visit to the next was higher in those reporting a sore throat during the dry season (OR 3.7, 95% CI 2.0-6.7) and lower in those reporting antibiotic use (OR 0.17, 95% CI 0.03-0.56). CONCLUSIONS: Acquisition of meningococcal carriage peaked in school age children. Recent symptoms of sore throat during the dry season, but not during the rainy season, were associated with a higher risk of acquisition. Upper respiratory tract infections may be an important driver of epidemics in the meningitis belt.

BACKGROUND: Serum bactericidal antibody titres that correlate with protection against invasive meningococcal disease have been characterised. However, titres that are associated with protection against acquisition of pharyngeal carriage of Neisseria meningitidis are not known. METHODS: Sera were obtained from the members of a household in seven countries of the African meningitis belt in which a pharyngeal carrier of N. meningitidis had been identified during a cross-sectional survey. Serum bactericidal antibody titres at baseline were compared between individuals in the household of the carrier who became a carrier of a meningococcus of the same genogroup during six months of subsequent follow-up and household members who did not become a carrier of a meningococcus of this genogroup during this period. RESULTS: Serum bacterial antibody titres were significantly higher in carriers of a serogroup W or Y meningococcus at the time of recruitment than in those who were not a carrier of N. meningitidis of the same genogroup. Serum bactericidal antibody titres to a strain of N. meningitis of the same genogroup as the index cases were no different in individuals who acquired carriage with a meningococcus of the same genogroup as the index case than in those who did not become a carrier during six months of follow-up. CONCLUSION: Serum bacterial antibody titres to N. meningitidis of genogroup W or Y in the range of those acquired by natural exposure to meningococci of these genogroups, or with cross-reactive bacteria, are not associated with protection against acquisition of carriage with meningococci of either of these genogroups.