Abstract
SummaryBackgroundIn the first 2 years after a nationwide mass vaccination campaign of 1–29-year-olds with a meningococcal serogroup A conjugate vaccine (MenAfriVac) in Burkina Faso, carriage and disease due to serogroup A Neisseria meningitidis were nearly eliminated. We aimed to assess the long-term effect of MenAfriVac vaccination on meningococcal carriage and herd immunity.MethodsWe did four cross-sectional studies of meningococcal carriage in people aged 9 months to 36 years in two districts of Burkina Faso between May 2, 2016, and Nov 6, 2017. Demographic information and oropharyngeal swabs were collected. Meningococcal isolates were characterised using whole-genome sequencing.FindingsOf 14 295 eligible people, 13 758 consented and had specimens collected and laboratory results available, 1035 of whom were meningococcal carriers. Accounting for the complex survey design, prevalence of meningococcal carriage was 7·60% (95% CI 5·67–9·52), including 6·98% (4·86–9·11) non-groupable, 0·48% (0·01–0·95) serogroup W, 0·10% (0·01–0·18) serogroup C, 0·03% (0·00–0·80) serogroup E, and 0% serogroup A. Prevalence ranged from 5·44% (95% CI 4·18–6·69) to 9·14% (6·01–12·27) by district, from 4·67% (2·71–6·64) to 11·17% (6·75–15·59) by round, and from 3·39% (0·00–8·30) to 10·43% (8·08–12·79) by age group. By clonal complex, 822 (88%) of 934 non-groupable isolates were CC192, all 83 (100%) serogroup W isolates were CC11, and nine (69%) of 13 serogroup C isolates were CC10217.InterpretationOur results show the continued effect of MenAfriVac on serogroup A meningococcal carriage, for at least 7 years, among vaccinated and unvaccinated cohorts. Carriage prevalence of epidemic-prone serogroup C CC10217 and serogroup W CC11 was low. Continued monitoring of N meningitidis carriage will be crucial to further assess the effect of MenAfriVac and inform the vaccination strategy for future multivalent meningococcal vaccines.FundingBill & Melinda Gates Foundation and Gavi, the Vaccine Alliance.
Highlights
In the first 2 years after a nationwide mass vaccination campaign of 1–29-year-olds with a meningococcal serogroup A conjugate vaccine (MenAfriVac) in Burkina Faso, carriage and disease due to serogroup A Neisseria meningitidis were nearly eliminated
Isolates from four participants with a preliminary result of N meningitidis from field testing in Burkina Faso were excluded from the analysis because no isolate was available for confirmatory testing at the Centers for Disease Control and Prevention (CDC) or Norwegian Institute of Public Health (NIPH)
Non-groupable meningococci accounted for 90·3% of all carriage, with a prevalence of 6·98%
Summary
In the first 2 years after a nationwide mass vaccination campaign of 1–29-year-olds with a meningococcal serogroup A conjugate vaccine (MenAfriVac) in Burkina Faso, carriage and disease due to serogroup A Neisseria meningitidis were nearly eliminated. Despite a more than 99% reduction in the incidence of serogroup A disease in MenAfriVac-vaccinated countries,[10] concerns about possible recrudescence of serogroup A N meningitidis in Burkina Faso resulting from waning MenAfriVac-induced immunity and sus ceptibility of unvaccinated new-birth cohorts, as well as emergence of novel, epidemic-prone strains of nonserogroup A N meningitidis, motivated implementation of a follow-up meningococcal carriage study during 2016–17. In the 2 years after the mass vaccination campaign, carriage and disease due to serogroup A were nearly eliminated in Burkina Faso, showing the impact of the vaccine on carriage, disease, and herd immunity.[3,4] in 2014–15, five cases of serogroup A meningococcal meningitis, as well as several cases of serogroup C meningococcal meningitis caused by a strain with molecular characteristics similar to the sequence type responsible for large meningococcal meningitis outbreaks in Niger and Nigeria (ST-10217), were reported in Burkina Faso; most of the serogroup A cases, along with several serogroup C cases, were detected in Ouahigouya district.[5,6,7,8,9]
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