Whom and where are we not vaccinating? Coverage after the introduction of a new conjugate vaccine against group A meningococcus in Niger in 2010.

Sung Hye Kim,Thomas F Wierzba,Harouna Yacouba,Mamoudou H Djingarey,Lorenzo Pezzoli,William A Perea,Tiekoura Coulibaly

doi:10.1371/journal.pone.0029116

Abstract

MenAfriVac is a new conjugate vaccine against Neisseria meningitidis serogroup A developed for the African “meningitis belt”. In Niger, the first two phases of the MenAfriVac introduction campaign were conducted targeting 3,135,942 individuals aged 1 to 29 years in the regions of Tillabéri, Niamey, and Dosso, in September and December 2010. We evaluated the campaign and determined which sub-populations or areas had low levels of vaccination coverage in the regions of Tillabéri and Niamey. After Phase I, conducted in the Filingué district, we estimated coverage using a 30×15 cluster-sampling survey and nested lot quality assurance (LQA) analysis in the clustered samples to identify which subpopulations (defined by age 1–14/15–29 and sex) had unacceptable vaccination coverage (<70%). After Phase II, we used Clustered Lot Quality Assurance Sampling (CLQAS) to assess if any of eight districts in Niamey and Tillabéri had unacceptable vaccination coverage (<75%) and estimated overall coverage. Estimated vaccination coverage was 77.4% (95%CI: 84.6–70.2) as documented by vaccination cards and 85.5% (95% CI: 79.7–91.2) considering verbal history of vaccination for Phase I; 81.5% (95%CI: 86.1–77.0) by card and 93.4% (95% CI: 91.0–95.9) by verbal history for Phase II. Based on vaccination cards, in Filingué, we identified both the male and female adult (age 15–29) subpopulations as not reaching 70% coverage; and we identified three (one in Tillabéri and two in Niamey) out of eight districts as not reaching 75% coverage confirmed by card. Combined use of LQA and cluster sampling was useful to estimate vaccination coverage and to identify pockets with unacceptable levels of coverage (adult population and three districts). Although overall vaccination coverage was satisfactory, we recommend continuing vaccination in the areas or sub-populations with low coverage and reinforcing the social mobilization of the adult population.

Highlights

The African ‘‘meningitis belt’’ is an area that stretches from Senegal to Ethiopia, where major epidemics of meningococcal meningitis regularly occur [1]
We evaluated the first two phases of the MenAfriVac introduction campaign in the regions of Tillaberi and Niamey in Niger using a combination of cluster-sampling and lot quality assurance sampling (LQAS) techniques
Overall vaccination coverage was 81% based on the availability of vaccination cards; 92% considering verbal report of vaccination as a reliable source of information

Summary

Introduction

The African ‘‘meningitis belt’’ is an area that stretches from Senegal to Ethiopia, where major epidemics of meningococcal meningitis regularly occur [1]. Neisseria meningitidis serogroup A is the primary cause of meningitis epidemics in the meningitis belt [2]. The human toll from these epidemics is enormous. In the 1996–1997 epidemics, more than 250,000 cases and 25,000 deaths were reported [3]. During the 2009 epidemic season, 14 countries reported a total of 78,416 cases, including 4,055 deaths. After Nigeria, Niger was the second most affected country [2]

Methods

Results

Conclusion