Serogroup A meningococcal conjugate vaccines in Africa

Abstract

Serogroup A meningococcal epidemics have been a recurrent public health problem, especially in resource-poor countries of Africa. Recently, the administration in mass vaccination campaigns of a single dose of the monovalent meningococcal conjugate vaccine, MenAfriVac, to the 1–29 year-old population of sub-Saharan Africa has prevented epidemics of meningitis caused by serogroup A Neisseria meningitidis. This strategy has also been shown to provide herd protection of the non-vaccinated population. Development of meningococcal conjugate vaccines covering other serogroups and enhanced use of the pneumococcal and Haemophilus influenzae type b conjugate vaccines must be pursued to fully control bacterial meningitis in sub-Saharan Africa.

Keywords:

• herd protection
• immunization
• invasive meningococcal disease
• MenAfriVac
• meningitis epidemic
• meningococcal carriage
• meningococcal conjugate vaccine
• vaccine coverage

Financial & competing interests disclosure

PA Kristiansen and HJ Jørgensen’s salaries are funded by the Research Council of Norway, grant no. 220829 to DA Caugant. PA Kristiansen and DA Caugant have collaborated with WHO, MVP and other international partners in research projects linked to MenAfriVac, such activities have been funded by own institution (NIPH) and the Research Council of Norway. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Key issues

• The greatest burden of meningococcal disease in the world is in the meningitis belt, which extends south of the Sahara from Senegal to Ethiopia, where major seasonal epidemics have been caused by Neisseria meningitidis belonging to serogroup A and the ST-5 clonal complex.

• The Meningitis Vaccine Project, which was launched in 2001, supported the Serum Institute of India Ltd. in developing a low cost PsA-TT conjugate vaccine, licensed as MenAfriVac in 2010.

• Clinical trials demonstrated that MenAfriVac is safe, induces a superior immune response compared to polysaccharide vaccines and provides immunological memory.

• MenAfriVac was introduced in 15 African countries in mass vaccination campaigns between 2010 and 2014, and so far, more than 217 million people have been vaccinated.

• The vaccination campaigns have significantly reduced the incidence of meningococcal disease. No disease cases caused by serogroup A N. meningitidis have been reported in vaccinated individuals.

• MenAfriVac vaccination has been shown to reduce carriage of serogroup A N. meningitidis and to induce herd protection.

• Long-term vaccination strategies must be implemented to maintain protection of the populations.

• Following introduction of MenAfriVac, meningococci belonging to other serogroups (C, W, X) have caused outbreaks of meningococcal disease.