Phenotypic and genotypic characterization of meningococcal carriage and disease isolates in Burkina Faso after mass vaccination with a serogroup a conjugate vaccine

Abstract

BackgroundThe conjugate vaccine against serogroup A Neisseria meningitidis (NmA), MenAfriVac, was first introduced in mass vaccination campaigns of the 1-29-year-olds in Burkina Faso in 2010. The aim of this study was to genetically characterize meningococcal isolates circulating in Burkina Faso before and up to 13 months after MenAfriVac mass vaccination.MethodsA total of 1,659 meningococcal carriage isolates were collected in a repeated cross-sectional carriage study of the 1-29-year-olds in three districts of Burkina Faso in 2010 and 2011, before and up to 13 months after mass vaccination. Forty-two invasive isolates were collected through the national surveillance in Burkina Faso in the same period. All the invasive isolates and 817 carriage isolates were characterized by serogroup, multilocus sequence typing and porA-fetA sequencing.ResultsSeven serogroup A isolates were identified, six in 2010, before vaccination (4 from carriers and 2 from patients), and one in 2011 from an unvaccinated patient; all were assigned to sequence type (ST)-2859 of the ST-5 clonal complex. No NmA carriage isolate and no ST-2859 isolate with another capsule were identified after vaccination. Serogroup X carriage and disease prevalence increased before vaccine introduction, due to the expansion of ST-181, which comprised 48.5% of all the characterized carriage isolates. The hypervirulent serogroup W ST-11 clone that was responsible for most of meningococcal disease in 2011 and 2012 was not observed in 2010; it appeared during the epidemic season of 2011, when it represented 40.6% of the serogroup W carriage isolates.ConclusionsSuccessive clonal waves of ST-181 and ST-11 may explain the changing epidemiology in Burkina Faso after the virtual disappearance of NmA disease and carriage. No ST-2859 strain of any serogroup was found after vaccination, suggesting that capsule switching of ST-2859 did not occur, at least not during the first 13 months after vaccination.

Narrative review of methods and findings of recent studies on the carriage of meningococci and other Neisseria species in the African Meningitis Belt

“…Although multiple porA‐fetA combinations were identified for all but serogroup A, one combination was found in the majority of isolates for each serogroup suggesting selection pressure for particular genetic traits. The surveys conducted in the same sites a year after MenAfriVac R vaccination identified mostly NmX belonging to ST‐181 (5.33% of the samples) . Two years after MenAfriVac R vaccination, Nm W from ST‐11 cc dominated with a carriage prevalence of 6.85% .…”

“…Twenty papers were identified which described meningococcal carriage surveys conducted in nine African meningitis belt countries and reported since 2007 [4][5][6][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Sixteen of these surveys were conducted prior to the deployment of the group A meningococcal conjugate vaccine (MenAfriVac â ).…”

Serogroup A meningococcal conjugate vaccines in Africa

“…Incidence peaked in 2011 during the first epidemic season after MenAfriVac introduction and the dominating clone was ST-181 [88], the same clone that had been responsible for outbreaks in Niger in 2006 [8] and was circulating among healthy Burkinabe carriers in 2009, 2010 and 2011 [81,88]. The proportion of meningitis cases assigned to serogroup X gradually declined in Burkina Faso, but in 2014, serogroup X again caused cases in Mali (TABLE 3).…”

“…To date, there are no reports of disease or carriage in Africa caused by a ST-5 clonal complex strain expressing another capsule than A. After MenAfriVac introduction, the few serogroup A strains that have been characterized were all assigned to the ST-5 clonal complex and none of the non-serogroup A strains have been assigned to ST-5 clonal complex [82,88] [UNPUB-LISHED DATA].…”

Glycoconjugate vaccines: an update

“…In the African meningitis belt, which is a region below the Sahara desert stretching from Senegal in the east to Ethiopia in the west, devastating epidemics of MenA disease occur every 8 --12 years [139,140] The need for a MenA conjugate vaccine potentially conferring lasting immunity and herd protection, which could not be provided by a plain polysaccharide MenA vaccine, has long been recognised. The introduction of MenA-TT, a tetanus toxoid MenA glycoconjugate vaccine (MenAfriVac, Serum Institute of India) in mass vaccination campaigns of 1 --29-year olds in Burkina Faso in 2010 was a major advance in the history of meningococcal vaccination within these hyperendemic areas [139].…”