Serogroup A meningococcal conjugate vaccination in Burkina Faso: analysis of national surveillance data

Background 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. Methods 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. Findings During the 14 year period before PsA-TT introduction, Burkina Faso had 148603 cases of suspected meningitis with 17965 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 100000 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). Interpretation 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.