Impact of MenAfriVac on Serogroup A Transmission and Clinical Evaluation of a New Protein-Based Vaccine, 2014

The bacterium Neisseria meningitidis is a significant cause of epidemic meningitis in sub-Saharan Africa. In the meningitis belt, an area which includes the poorest countries of the world. N. meningitidis serogroup A has been responsible for major epidemics for several decades. A new serogroup A conjugate vaccine, MenAfriVac, was introduced in parts of Ethiopia in 2013. The project implemented molecular diagnostics in the two major laboratories in Addis Ababa. In addition the prevalence of asymptomatic carriage and serogroup distribution of N. meningitidis in Ethiopia prior to MenAfriVac introduction were assessed. 7479 throat samples were collected and an overall carriage prevalence of 6.6% was found. No serogroup A isolates were identified. Thus, the immediate impact of mass-vaccination with MenAfriVac on transmission of N. meningitidis in this population was expected to be marginal. Some of the carriers were followed over an eight-week period to assess the impact of conjugate vaccines on carriage and antibody levels in saliva and serum. Bacterial isolates were characterized using whole genome sequencing to investigate the within-host genomic changes. IgG and IgA antibodies were analyzed in serum and saliva samples. The meningococcal conjugate vaccines were able to elicit salivary antibodies correlating with antibody levels in serum.