Meningococcal Seroepidemiology 1 Year After the PsA-TT Mass Immunization Campaign in Burkina Faso

Abstract

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.

Keywords: Neisseria meningitidis; conjugate; group A; seroepidemiologic studies; sub-Saharan Africa.

Figure 1.

Age-specific vaccination coverage with meningococcal group A conjugate vaccine in Bobo-Dioulasso, Burkina Faso, 2011. Estimates are given for all study participants, and specifically for participants who were residents of Bobo-Dioulasso in 2010 according to different information types.

Figure 2.

Seroprevalence according to different serologic outcomes among the population aged 23 months to 29 years, by age group, Bobo-Dioulasso, Burkina Faso, 2011. Included are all 481 study participants who were eligible for meningococcal group A conjugate vaccination during 2010. Abbreviations: anti-A, against meningococcal serogroup A; IgG, immunoglobulin G; SBA, serum bactericidal antibody.