Neisseria meningitidis serogroups A and W-135:: Carriage and immunity in Burkina Faso, 2003

Objectives. We sought to describe Neisseria meningitidis immunity and its association with pharyngeal carriage in Burkina Faso, where N. meningitidis serogroup W-135 and serogroup A disease are hyperendemic and most of the population received polysaccharide A/C vaccine during 2002. Methods. We collected oropharyngeal swab samples from healthy residents of Bobo-Dioulasso (4-14 years old,; 15-29 years old,) monthly during February-June 2003; N. meningitidis isolates were analyzed n= 238 n = 250 using polymerase chain reaction and serogrouped using immune sera. Serum samples were collected at the first and last clinic visit and analyzed for anti-A, anti-C, anti-W-135, and anti-Y immunoglobulinG(IgG) concentrations and anti-A and anti-W-135 bactericidal titers. Results. N. meningitidis was carried at least once by 18% of participants; this carriage included strains from serogroups W-135 (5%) and Y and X ( both < 1%) but not from serogroups A, B, or C. At baseline, the prevalence of putatively protective specific IgG concentrations (>= 2 mg/mL) and bactericidal titers (>= 8) was 85% and 54%, respectively, against serogroup A, and 6% and 22%, respectively, against serogroup W-135. Putatively protective anti-W-135 IgG concentrations and bactericidal titers were of short duration and were not associated with carriage. Conclusion. N. meningitidis serogroup W-135 strains did not induce immunity, despite their circulation. Carriage of serogroup A strains was rare despite the hyperendemic incidence of serogroup A meningitis during 2003 in Bobo-Dioulasso. A vaccine that includes serogroup W-135 antigen and eliminates serogroup A carriage is needed for sub-Saharan Africa.