Efficacy and Effectiveness of the Meningococcal Conjugate Group A Vaccine MenAfriVac® in Preventing Recurrent Meningitis Epidemics in Sub-Saharan Africa

Abstract

For more than a century, epidemic meningococcal disease mainly caused by serogroup A Neisseria meningitidis has been an important public health problem in sub-Saharan Africa. To address this problem, an affordable meningococcal serogroup A conjugate vaccine, MenAfriVac^®, was developed specifically for populations in the African meningitis belt countries. MenAfriVac^® was licensed based on safety and immunogenicity data for a population aged 1-29 years. In particular, the surrogate markers of clinical efficacy were considered to be the higher immunogenicity and the ability to prime immunological memory in infants and young children compared to a polysaccharide vaccine. Because of the magnitude of serogroup A meningitis epidemics and the high morbidity and mortality burden, the World Health Organization (WHO) recommended the MenAfriVac^® deployment strategy, starting with mass vaccination campaigns for 1-29-year-olds to rapidly interrupt serogroup A person-to-person transmission and establish herd protection, followed by routine immunization of infants and toddlers to sustain protection and prevent epidemics. After licensure and WHO prequalification of MenAfriVac^®, campaigns began in December 2010 in Burkina Faso, Mali, and Niger. By the middle of 2011, it was clear that the vaccine was highly effective in preventing serogroup A carriage and disease. Post introduction meningitis surveillance revealed that serogroup A meningococcal disease had disappeared from all age groups, suggesting that robust herd immunity had been achieved.

Keywords: Neisseria meningitidis serogroup A; conjugate meningococcal vaccine; effectiveness; efficacy; meningitis epidemic; sub-Saharan Africa.

Figure 1

Areas with frequent epidemics of meningococcal meningitis. Disease data source: World Health Organization, International Travel and Health (Geneva, Switzerland, 2015). https://wwwnc.cdc.gov/travel/yellowbook/2020/travel-related-infectious-diseases/meningococcal-disease (accessed 23 March 2022).

Figure 2

MenAfriVac^® introduction in the meningitis belt countries, 2010–2021. From WHO/IST-WA Meningitis Weekly Bulletin, 2021 (https://cdn.who.int/media/docs/default-source/2021-dha-docs/bulletin-meningite_s26_2021.pdf?sfvrsn=3512cc8e_1&download=true) (accessed 22 March 2022).