Meningococcal seroepidemiology 1 year after the PsA-TT mass immunization campaign in Burkina Faso

Background. A group A meningococcal (MenA) conjugate vaccine, PsA-TT (MenAfriVac), was introduced in Burkina Faso via mass campaigns between September and December 2010, targeting the 1- to 29-year-old population. This study describes specific antibody titers in the general population 11 months later and compares them to preintroduction data obtained during 2008 using the same protocol. Methods. During October-November 2011, we recruited a representative sample of the population of urban Bobo-Dioulasso aged 6 months to 29 years, who underwent standardized interviews and blood draws. We assessed anti-MenA immunoglobulin G (IgG) concentrations (n = 200) and, using rabbit complement, serum bactericidal antibody (SBA) titers against 2 group A strains: reference strain F8238 (SBAref) (n = 562) and strain 3125 (SBA3125) (n = 200). Results. Among the 562 participants, 481 (86%) were aged ≥23 months and had been eligible for the PsA-TT campaign. Among them, vaccine coverage was 86.3% (95% confidence interval [CI], 82.7%-89.9%). Prevalence of putatively protective antibodies among vaccine-eligible age groups was 97.3% (95% CI, 95.9%-98.7%) for SBAref titers ≥128, 83.6% (95% CI, 77.6%-89.7%) for SBA3125 ≥128, and 84.2% (95% CI, 78.7%-89.7%) for anti-MenA IgG ≥2 μg/mL. Compared to the population aged 23 months to 29 years during 2008, geometric mean titers of SBAref were 7.59-fold higher during 2011, 51.88-fold for SBA3125, and 10.56-fold for IgG. Conclusions. This study shows high seroprevalence against group A meningococci in Burkina Faso following MenAfriVac introduction. Follow-up surveys will provide evidence on the persistence of population-level immunity and the optimal vaccination strategy for long-term control of MenA meningitis in the African meningitis belt.