Monitoring adverse events following immunization with a new conjugate vaccine against group A meningococcus in Niger, September 2010

Abstract

Introduction: MenAfriVac is a new conjugate vaccine against Neisseria meningitidis serogroup A, the major cause of meningitis outbreaks in sub-Saharan Africa. In Niger, the MenAfriVac introduction campaign was conducted in the District of Filingue, during September 2010, targeting 392,211 individuals aged 1-29 years. We set up an enhanced spontaneous surveillance system to monitor adverse events following immunization (AEFI) during the campaign period and 42 days thereafter.

Methods: All the 33 health centres of the district have been designated as surveillance units, which reported AEFIs on a daily basis to the health district headquarters. Health care workers were instructed to screen patients presenting with predefined conditions of interest and patients spontaneously presenting at units or at vaccination posts with complaints after vaccination. Cases were classified as serious (resulting in death, hospitalization or long-term disability) or minor. A National Expert Committee was established to determine if serious cases were causally associated with the vaccine.

Results: In total, 356,532 vaccine doses were administered. During 61 days of monitoring, 82 suspected AEFIs were reported: 16 severe and 66 minor. The cumulative incidence was of 23.0 per 100,000 doses. Among severe cases, 14 were classified as coincidences, one urticaria complicated by respiratory distress was classified as a probable vaccine reaction, and one death was unclassifiable because post-mortem information was unavailable. The number of units that reported at least one case was 19/33 (57.6%).

Conclusions: Although these results are limited by underreporting of cases, we did not identify safety concerns with MenAfriVac. The lessons learned from this experience should be used to reinforce the national pharmacovigilance system in Niger to make it complaint with international standards. In order to do so, we recommend using a lighter system for routine; and conducting regular training and supervisory activities to increase its acceptance among local health workers.