Meningoccal Vaccines

Neisseria meningitidis causes different types of clinical conditions. Among these meningococcemia and bacterial meningitis are the two most frequent and dangerous. These two forms are termed invasive meningococcal disease. For the countries where the Haemophilus influenzae and the pneumococcal vaccines are in the routine vaccination schedules, N. meningitidis has become the leading pathogen of bacterial meningitis and community acquired sepsis. Meningococcus is still sensitive to many of the routinely used antibiotics including the penicillins and antibiotic resistance is not a significant problem for the treatment of the disease. The mortality of invasive meningococcal disease is 10-14% and the morbidity is high with 11-19% of survivors having sequelae including neurological disability, severe scar tissue of the skin, hearing loss and limb loss. There are several types of vaccines available for N. meningitidis. However, currently, there is no vaccine available for use in early infancy which can provide long term protection for all serogroups that can cause disease,but research to produce a vaccine with these properties is ongoing. The meningococcal vaccines available now are either polysaccharide vaccines or conjugate vaccines. The polysaccharide vaccines are produced by purification of the polysaccharide in the capsule of the meningococcus. The conjugate vaccines are produced by conjugating the capsular polysaccharides with different proteins. Currently, monovalent, bivalent and tetravalent polysaccharide and conjugate vaccines for the serogroups A, C, Y and W-135 are available. The immunogenicity of the capsular polysaccharide of the serogroup B is low, therefore it has not been possible to develop a vaccine using the capsular polysaccharide of this serogroup.However, there is ongoing research to produce a vaccine for serogroup B using other structural proteins.