Population-level persistence of immunity 2 years after the PsA-TT mass-vaccination campaign in Mali

Nicole E. Basta, Ray Borrow, Abdoulaye Berthe, Awa Traoré Eps Dembélé, Uma Onwuchekwa, Kelly Townsend, Rahamatou M. Boukary, Lesley Mabey, Helen Findlow, Xilian Bai, Samba O. Sow

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2 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)S547-S553
JournalClinical Infectious Diseases
StatePublished - Nov 15 2015

Bibliographical note

Publisher Copyright:
© 2015 The Author. Published by Oxford University Press on behalf of the Infectious Diseases Society of America.


  • Africa
  • immunity
  • meningococcal vaccines
  • seroprevalence


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