The Lancet Infectious Disease
Oct 2012 Volume 12 Number 10 p737 – 816 e1
A vaccine to prevent epidemic meningitis in Africa
Brian Greenwood, James M Stuart
Epidemics of meningococcal meningitis continue to occur at frequent but irregular intervals in countries of the African meningitis belt.1 Most of these large epidemics are caused by meningococci belonging to serogroup A. For the past three decades, control of epidemic meningitis in Africa has relied on reactive vaccination initiated only after the incidence of meningitis in a particular district or region has passed the epidemic threshold.2 This approach has prevented many cases but it has not reduced the frequency of epidemics because the polysaccharide vaccines used in these campaigns are poorly immunogenic in young children, do not induce immunological memory, and have little or no effect on pharyngeal carriage.
Serogroup A meningococcal conjugate vaccination in Burkina Faso: analysis of national surveillance data
Ryan T Novak, Jean Ludovic Kambou, Fabien VK Diomandé, Tiga F Tarbangdo, Rasmata Ouédraogo-Traoré, Lassana Sangaré, Clement Lingani, Stacey W Martin, Cynthia Hatcher, Leonard W Mayer, F Marc LaForce, Fenella Avokey, Mamoudou H Djingarey, Nancy E Messonnier, Sylvestre R Tiendrébéogo, Thomas A Clark
An affordable, highly immunogenic Neisseria meningitidis serogroup A meningococcal conjugate vaccine (PsA—TT) was licensed for use in sub-Saharan Africa in 2009. In 2010, Burkina Faso became the first country to implement a national prevention campaign, vaccinating 11·4 million people aged 1—29 years. We analysed national surveillance data around PsA—TT introduction to investigate the early effect of the vaccine on meningitis incidence and epidemics.
We examined national population-based meningitis surveillance data from Burkina Faso using two sources, one with cases and deaths aggregated at the district level from 1997 to 2011, and the other enhanced with results of cerebrospinal fluid examination and laboratory testing from 2007 to 2011. We compared mortality rates and incidence of suspected meningitis, probable meningococcal meningitis by age, and serogroup-specific meningococcal disease before and during the first year after PsA—TT implementation. We assessed the risk of meningitis disease and death between years.
During the 14 year period before PsA—TT introduction, Burkina Faso had 148,603 cases of suspected meningitis with 17,965 deaths, and 174 district-level epidemics. After vaccine introduction, there was a 71% decline in risk of meningitis (hazard ratio 0.29, 95% CI 0.28—0.30, p<0·0001) and a 64% decline in risk of fatal meningitis (0.36, 0.33—0.40, p<0·0001). We identified a statistically significant decline in risk of probable meningococcal meningitis across the age group targeted for vaccination (62%, cumulative incidence ratio [CIR] 0.38, 95% CI 0.31—0.45, p<0.0001), and among children aged less than 1 year (54%, 0.46, 0.24—0.86, p=0.02) and people aged 30 years and older (55%, 0.45, 0.22—0.91, p=0.003) who were ineligible for vaccination. No cases of serogroup A meningococcal meningitis occurred among vaccinated individuals, and epidemics were eliminated. The incidence of laboratory-confirmed serogroup A N meningitidis dropped significantly to 0.01 per 100,000 individuals per year, representing a 99.8% reduction in the risk of meningococcal A meningitis (CIR 0.002, 95% CI 0.0004—0.02, p<0.0001).
Early evidence suggests the conjugate vaccine has substantially reduced the rate of meningitis in people in the target age group, and in the general population because of high coverage and herd immunity. These data suggest that fully implementing the PsA—TT vaccine could end epidemic meningitis of serogroup A in sub-Saharan Africa.