Meningococcal carriage and cerebrospinal meningitis after MenAfriVac mass immunization in Burkina Faso

Abstract

The aims of this study were to evaluate the impact of conjugate vaccine A, MenAfriVac, on Neisseria meningitidis (Nm) asymptomatic carriage and cerebrospinal meningitis in three health districts (Bogodogo, Kaya, and Dandé) of Burkina Faso. Asymptomatic carriage of Nm was assessed by performing cross-sectional studyrepeated (rounds 1 to 10) before and after introduction of the conjugate vaccine against serogroup A of N. meningitidis (NmA), MenAfriVac. In each round at least 1,500 people were enrolled in each district for a month. Data oncases of meningococcal meningitis in the three studied health districts were collected through meningitides epidemiological surveillance of Burkina Faso.Nm was identified in680 of 23,885 throat swabs before vaccination (2. 84%)withNmYasthe dominant serogroup(1.87%). During the same period (2009 and 2010), 891 cases of suspected meningitis were reported in the three health districts among whom 42 were due toNm (4.71%) withNmX (3.70%) asthe most frequently identified serogroup. After vaccination, Nm was identified in 1117 of 27,245 pharyngeal samples (6.42%); NmX (4.42%) wasthe dominantserogroup. From 2011 to 2013, 965 cases of suspected meningitis were reported in all health facilities in the three studied health districts located in the geographical study area; 91 was due toNm (9.43%) andNmWasthe most commonserogroup(52 cases= 5.38%).After introduction of conjugate vaccine A (MenAfriVac), the NmAserogroup almost disappeared both in asymptomatic carriers and in patients with cerebrospinal meningitis. However the presence of the NmW and NmXserogroups, which appear to have replaced serogroup A, is very worrying with regard to meningitis prevention and control in Burkina Faso. It appears necessary to strengthen surveillance and laboratory diagnosis of the different meningococcal serogroups circulating in Africa.

Keywords: meningococcal meningitis, serogroups W and X, meningococcal carriage, MenAfriVac.