title: Population-Level Persistence of Immunity 2 Years After the PsA-TT Mass-Vaccination Campaign in Mali.
abstract: BACKGROUND
  In 2010, Africa's first preventive meningococcal mass vaccination campaign was launched using a newly developed Neisseria meningitidis group A (NmA) polysaccharide-tetanus toxoid conjugate vaccine, PsA-TT (MenAfriVac), designed specifically for the meningitis belt. Given PsA-TT's recent introduction, the duration of protection against meningococcal group A is unknown.
  
  
  METHODS
  We conducted a household-based, age-stratified seroprevalence survey in Bamako, Mali, in 2012, 2 years after the vaccination campaign targeted all 1- to 29-year-olds. Randomly selected participants who had been eligible for PsA-TT provided a blood sample and responded to a questionnaire. Sera were analyzed to assess NmA-specific serum bactericidal antibody titers using rabbit complement (rSBA) and NmA-specific immunoglobulin G (IgG) by enzyme-linked immunosorbent assay. The proportion of participants putatively protected and the age group- and sex-specific rSBA geometric mean titers (GMTs) and IgG geometric mean concentrations (GMCs) were determined.
  
  
  RESULTS
  Two years postvaccination, nearly all of the 800 participants (99.0%; 95% confidence interval [CI], 98.3%-99.7%) maintained NmA-specific rSBA titers ≥8, the accepted threshold for protection; 98.6% (95% CI, 97.8%-99.4%) had titers ≥128, and 89.5% (95% CI, 87.4%-91.6%) had titers ≥1024. The rSBA GMTs were significantly higher in females than in males aged <18 years at vaccination (P < .0001). NmA-specific IgG levels ≥2 µg/mL were found in 88.5% (95% CI, 86.3%-90.7%) of participants.
  
  
  CONCLUSIONS
  Two years after PsA-TT introduction, a very high proportion of the population targeted for vaccination maintains high antibody titers against NmA. Assessing the duration of protection provided by PsA-TT is a priority for implementing evidence-based vaccination strategies. Representative, population-based seroprevalence studies complement clinical trials and provide this key evidence.
authors.affiliation: Division of Epidemiology and Community Health, University of Minnesota, Minneapolis Fogarty International Center, National Institutes of Health, Bethesda, Maryland.
authors.forename: Nicole E
authors.initials: NE
authors.lastname: Basta
authors.affiliation: Vaccine Evaluation Unit, Public Health England, Manchester Royal Infirmary, United Kingdom.
authors.forename: Ray
authors.initials: R
authors.lastname: Borrow
authors.affiliation: Centre pour le Développement des Vaccins, Ministère de la Santé, Bamako, Mali.
authors.forename: Abdoulaye
authors.initials: A
authors.lastname: Berthe
authors.affiliation: Centre pour le Développement des Vaccins, Ministère de la Santé, Bamako, Mali.
authors.forename: Awa Traoré Eps
authors.initials: AT
authors.lastname: Dembélé
authors.affiliation: Centre pour le Développement des Vaccins, Ministère de la Santé, Bamako, Mali.
authors.forename: Uma
authors.initials: U
authors.lastname: Onwuchekwa
authors.affiliation: Vaccine Evaluation Unit, Public Health England, Manchester Royal Infirmary, United Kingdom.
authors.forename: Kelly
authors.initials: K
authors.lastname: Townsend
authors.affiliation: Vaccine Evaluation Unit, Public Health England, Manchester Royal Infirmary, United Kingdom.
authors.forename: Rahamatou M
authors.initials: RM
authors.lastname: Boukary
authors.affiliation: Vaccine Evaluation Unit, Public Health England, Manchester Royal Infirmary, United Kingdom.
authors.forename: Lesley
authors.initials: L
authors.lastname: Mabey
authors.affiliation: Vaccine Evaluation Unit, Public Health England, Manchester Royal Infirmary, United Kingdom.
authors.forename: Helen
authors.initials: H
authors.lastname: Findlow
authors.affiliation: Vaccine Evaluation Unit, Public Health England, Manchester Royal Infirmary, United Kingdom.
authors.forename: Xilian
authors.initials: X
authors.lastname: Bai
authors.affiliation: Centre pour le Développement des Vaccins, Ministère de la Santé, Bamako, Mali.
authors.forename: Samba O
authors.initials: SO
authors.lastname: Sow
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D001770:Blood Bactericidal Activity; D002648:Child; D002675:Child, Preschool; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007223:Infant; D008297:Male; D008302:Mali / Q000453:epidemiology; D008585:Meningitis, Meningococcal / Q000453:epidemiology / Q000517:prevention & control*; D022401:Meningococcal Vaccines / Q000008:administration & dosage / Q000276:immunology*; D038381:Neisseria meningitidis, Serogroup A / Q000276:immunology*; D016036:Seroepidemiologic Studies; D011795:Surveys and Questionnaires; D013997:Time Factors; D055815:Young Adult
chemical_list: D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; C573970:MenAfriVac; D022401:Meningococcal Vaccines
keywords: Africa; immunity; meningococcal vaccines; seroprevalence