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Response Strategies against Meningitis Epidemics after Elimination of Serogroup A Meningococci, Niger - Volume 21, Number 8—August 2015 - Emerging Infectious Disease journal - CDC

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Response Strategies against Meningitis Epidemics after Elimination of Serogroup A Meningococci, Niger - Volume 21, Number 8—August 2015 - Emerging Infectious Disease journal - CDC

Volume 21, Number 8—August 2015


Response Strategies against Meningitis Epidemics after Elimination of Serogroup A Meningococci, Niger

Halima Boubacar MaïnassaraComments to Author , Juliette Paireau, Issa Idi, Jean-Paul Moulia Pelat, Odile Ouwe Missi Oukem-Boyer, Arnaud Fontanet, and Judith E. Mueller
Author affiliations: Université Pierre et Marie Curie, Paris (H.B. Maïnassara, J. Paireau)Institut Pasteur, Paris, France (H.B. Maïnassara, J. Paireau, A. Fontanet, J.E. Mueller)Centre de Recherche Médicale et Sanitaire, Niamey, Niger (H.B. Maïnassara, I. Idi, J.-P.M. Pelat, O.O.M. Oukem-Boyer)Chaire Santé et Développement, Paris (A. Fontanet)Ecole des Hautes Études en Santé Publique, Rennes, France (J.E. Mueller)


To inform epidemic response strategies for the African meningitis belt after a meningococcal serogroup A conjugate vaccine was introduced in 2010, we compared the effectiveness and efficiency of meningitis surveillance and vaccine response strategies at district and health area levels using various thresholds of weekly incidence rates. We analyzed reports of suspected cases from 3 regions in Niger during 2002–2012 (154,392 health area weeks), simulating elimination of serogroup A meningitis by excluding health area years with identification of such cases. Effectiveness was highest for health area surveillance and district vaccination (58–366 cases; thresholds 7–20 cases/100,000 doses), whereas efficiency was optimized with health area vaccination (5.6–7.7 cases/100,000 doses). District-level intervention prevented <6 cases (0.2 cases/100,000 doses). Reducing the delay between epidemic signal and vaccine protection by 2 weeks doubled efficiency. Subdistrict surveillance and response might be most appropriate for meningitis epidemic response after elimination of serogroup A meningitis.
For several decades, epidemic meningitis has been a major health problem in the African meningitis belt.Neisseria meningitidis serogroup A (NmA) has been responsible for most localized epidemics or epidemic waves, and other meningococcal serogroups occasionally caused epidemics (1,2). After the introduction of an NmA conjugate vaccine (PsA-TT, MenAfrivac; Serum Institute of India Ltd., Hadapsar, Pune, India), implemented since 2010 in mass campaigns focused on persons 1–29 years of age, no epidemics caused by NmA have occurred in countries where the vaccine is administered (i.e., vaccinated countries). Seasonal hyperendemicity continues to occur during the dry season because of meningococci and pneumococci in similar proportions (3), and NmA has been identified only exceptionally (4,5). So far, epidemic control measures have consisted of reactive vaccination campaigns in epidemic districts by using serogroup A/C or A/C/W polysaccharide vaccines combined with adapted treatment protocols. To detect epidemics, national routine surveillance of suspected cases of acute bacterial meningitis has been conducted in all meningitis belt countries according to World Health Organization (WHO) guidelines (1), although the recommendation of splitting large districts (>100,000 inhabitants) into subdistricts is not always followed. Districts notifying weekly incidences of 5 cases/100,000 persons were considered in alert, and those notifying weekly incidences of 15 cases/100,000 persons were considered in epidemic (6); however, specific conditions enabled declaration of an epidemic at a threshold of 10 cases/100,000 persons.
Since PsA-TT was introduced in 2010, NmA incidence has been substantially lower than historical levels, and no replacement by other serogroups has been observed (7). Consequently, the overall incidence of suspected meningitis cases has declined in all vaccinated countries, and established surveillance and vaccination strategies might no longer be appropriate. Epidemic detection and response remains important because serogroups W and X have epidemic potential (1,2,4,8,9). A polysaccharide vaccine is available against N. meningitidis serogroup W (NmW); vaccines for serogroup X (NmX) are under development. NmA epidemics might continue to occur, requiring mass vaccination campaigns with PsA-TT.
One approach to adapting epidemic response strategies to the changing epidemiology is to lower the weekly incidence thresholds to <10 cases/100,000 persons, which would increase the risk for an increased number of false alerts in small districts. Another approach is to analyze surveillance data at a finer spatial scale than district level. As in Burkina Faso (2,10) and Niger (11), epidemics of any serogroup usually are highly localized in few neighboring health centers, whereas most health centers in the district in question remain (hyper-)endemic. District-level incidences are therefore diluted and may hide epidemic activity. Consequently, surveillance at the health center level could detect epidemics earlier and enable targeting of reactive vaccination, making the overall strategy more effective and efficient. Early epidemic detection through surveillance at the health center level could increase the effectiveness and efficiency of response strategies, particularly in the anticipated situation of eliminated NmA meningitis and overall reduced meningitis incidence.
Therefore, during 2002–2012, we evaluated the effectiveness and efficiency of surveillance and vaccine response strategies in Niger using various epidemic thresholds and comparing health area and district intervention. Our analysis was based on surveillance data of suspected and confirmed cases and considered 2 scenarios: the historical situation before PsA-TT introduction (PsA-TT was introduced in Niger in 3 phases: the first in August 2010, the second in November 2010, and the third in October 2011) and a simulation of NmA elimination.
Dr. Maïnassara is a medical doctor with a master’s degree in epidemiology working at the Centre de Recherche Médicale et Sanitaire of Niamey. Her primary research interest is bacterial meningitis.


We acknowledge the contribution of all the staff of the Centre de Recherche Médicale et Sanitaire and all health centers in Niger who participated in meningitis surveillance, the Direction de la Surveillance et de la Riposte aux Epidémies, the Direction des Statistiques, the Institut National de la Statistique, WHO, and the United Nations International Children's Emergency Fund. We are also grateful to Jean-François Jusot, Abaché Ranoua, Adakal Aboubacar, Maman Zaneidou, Noémie Phulpin, and Oumarou Alto for input into the project, assistance with data compilation and creation of health area maps.
H.B.M. and J.E.M. contributed substantially to the conception of the work; H.B.M., I.I., J-P.M.P., O.O.M.O.-B., and A.F. acquired the data; H.B.M., J.P., and J.E.M. analyzed and interpreted the data; H.B.M. drafted the manuscript; J.P., I.I., J.M., O.O., A.F., and J.E.M. conducted the critical revision of the work for important intellectual content; H.B.M., J.P., I.I., J-P.M.P., O.O.M.O.-B., A.F., and J.E.M. gave final approval of the version submitted and agree to be accountable for all aspects of the work.
This work was supported by the Office of International Cooperation of the Principality of Monaco. Surveillance activities were funded by the Ministère Français des Affaires Etrangères (Fonds de Solidarité Prioritaire), Sanofi Pasteur, and the Ministère de la Santé Publique du Niger/Fonds Commun. The first health area map was funded by Cooperation Technique Belge.


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Technical Appendix

Suggested citation for this article: Maïnassara HB, Paireau J, Idi I, Pelat JPM, Oukem-Boyer OOM, Fontanet A, et al. Response strategies against meningitis epidemics after elimination of serogroup A meningococci, Niger. Emerg Infect Dis. 2015 Aug [date cited].
DOI: 10.3201/eid2108.141361

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