Polysaccharide & conjugate vaccines
Two types of meningococcal vaccines useful in the African epidemiological context are available globally- polysaccharide vaccines and conjugate vaccines. Polysaccharide vaccines exist in various combinations against groups A, C, W135, and Y. These vaccines have existed for over 30 years and are highly effective in preventing disease in older children and adults and have been also used in reactive mass vaccination campaigns in Africa. However, these polysaccharide vaccines have several shortcomings that preclude their incorporation into routine immunization programs:

• They do not protect infants

• They provide protection for only two to three years, and

• They do not decrease carriage of the bacteria and do not induce herd immunity

Therefore, polysaccharide vaccines are mainly used either to control outbreaks or to protect travelers going to countries affected by the disease. In Africa, repeated vaccinations of the broadly targeted age group are logistically very difficult. Therefore, a monovalent group A conjugate vaccine providing longer-term protection for all ages and conferring herd immunity would be far better suited for the prevention of meningococcal epidemics. The conjugation process has been used to develop several meningitis vaccines, including several group C meningococcal vaccines, a Haemophilus influenza type b (Hib) vaccine, and a pneumococcal vaccine. Using the same conjugation technology, it has been possible to produce polysaccharide-protein conjugate vaccines for use in Africa. Benefits of the conjugate vaccine include:

• Protection for very young children

• Longer-lasting protection (effective for 10 years), and

• Decreased bacterial carriage inducing herd immunity, thereby protecting the unvaccinated population.

Finally, in June 2010, MenAfriVac™, the meningococcal group A conjugate vaccine developed through the Meningitis Vaccine Project (MVP) and produced at the Serum Institute of India Ltd. (SIIL), was prequalified by the World Health Organizaion (WHO). SIIL had received marketing authorization for export and use of MenAfriVac™ in Africa for US $0.40 per dose in early 2010. With WHO's prequalification in hand, the group A meningococcal conjugate vaccine could be introduced into Niger by multiple phased mass-immunization campaigns.

Reference:
J. Robbins et al, A rebuttal: epidemic and endemic meningococcal meningitis in sub-Saharan Africa can be prevented now by routine immunization with group A meningococcal capsular polysaccharide vaccine. Pediatric Infectious Disease Journal, 2000, 19(10): pp 945-953