The Lancet  
Jan 04, 2014  Volume 383  Number 9911  p1 – 98  e1 – 2
http://www.thelancet.com/journals/lancet/issue/current

Comment
Loosening the grip of meningococcal disease in Africa
Johannes Elias
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Although incidence rates of meningococcal disease in developed countries have steadily decreased over the past century, the disease remains a formidable public health threat in Africa. The geographical area most affected has been named the meningitis belt and includes countries of the Sahel and sub-Sahel. New findings from the study by Doumagoum Daugla and colleagues1 in The Lancet confirm the effectiveness of one shot of a glycoconjugate vaccine (serogroup A meningococcal polysaccharide–tetanus toxoid conjugate vaccine [PsA–TT, MenAfriVac]), developed under the Meningitis Vaccine Project (MVP),2 against disease caused by and carriage of serogroup A meningococci in Chad.

Effect of a serogroup A meningococcal conjugate vaccine (PsA—TT) on serogroup A meningococcal meningitis and carriage in Chad: a community study
DM Daugla MD a, JP Gami MSc a, K Gamougam TSL a, N Naibei MSc a, L Mbainadji PhD a, M Narbé TSL a, J Toralta MD a, B Kodbesse MD a, C Ngadoua TSSP b, ME Coldiron MD c, F Fermon DIU c, A-L Page PhD c, MH Djingarey MD d, S Hugonnet MD e, OB Harrison PhD f, LS Rebbetts MSc f, Y Tekletsion MSc f, ER Watkins BA f, D Hill BA f, DA Caugant PhD g, D Chandramohan PhD i, M Hassan-King PhD i, O Manigart PhD i, M Nascimento PhD i, A Woukeu PhD i, C Trotter PhD h, JM Stuart FFPH i, MCJ Maiden PhD f, Prof BM Greenwood MD i
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2813%2961612-8/abstract

Summary
Background
A serogroup A meningococcal polysaccharide—tetanus toxoid conjugate vaccine (PsA—TT, MenAfriVac) was licensed in India in 2009, and pre-qualified by WHO in 2010, on the basis of its safety and immunogenicity. This vaccine is now being deployed across the African meningitis belt. We studied the effect of PsA—TT on meningococcal meningitis and carriage in Chad during a serogroup A meningococcal meningitis epidemic.

Methods
We obtained data for the incidence of meningitis before and after vaccination from national records between January, 2009, and June, 2012. In 2012, surveillance was enhanced in regions where vaccination with PsA—TT had been undertaken in 2011, and in one district where a reactive vaccination campaign in response to an outbreak of meningitis was undertaken. Meningococcal carriage was studied in an age-stratified sample of residents aged 1—29 years of a rural area roughly 13—15 and 2—4 months before and 4—6 months after vaccination. Meningococci obtained from cerebrospinal fluid or oropharyngeal swabs were characterised by conventional microbiological and molecular methods.

Findings
Roughly 1·8 million individuals aged 1—29 years received one dose of PsA—TT during a vaccination campaign in three regions of Chad in and around the capital N’Djamena during 10 days in December, 2011. The incidence of meningitis during the 2012 meningitis season in these three regions was 2·48 per 100 000 (57 cases in the 2·3 million population), whereas in regions without mass vaccination, incidence was 43·8 per 100 000 (3809 cases per 8·7 million population), a 94% difference in crude incidence (p<0·0001), and an incidence rate ratio of 0·096 (95% CI 0·046—0·198). Despite enhanced surveillance, no case of serogroup A meningococcal meningitis was reported in the three vaccinated regions. 32 serogroup A carriers were identified in 4278 age-stratified individuals (0·75%) living in a rural area near the capital 2—4 months before vaccination, whereas only one serogroup A meningococcus was isolated in 5001 people living in the same community 4—6 months after vaccination (adjusted odds ratio 0·019, 95% CI 0·002—0·138; p<0·0001).

Interpretation
PSA—TT was highly effective at prevention of serogroup A invasive meningococcal disease and carriage in Chad. How long this protection will persist needs to be established.

Funding
The Bill & Melinda Gates Foundation, the Wellcome Trust, and Médecins Sans Frontères.