Meningococcal meningitis

Introduction on meningococcal disease

 Meningococcal disease is a life-threatening bacterial infection caused by Neisseria meningitidis, also known as meningococcus, which most commonly presents with meningitis and/or sepsis. Meningococci are classified into serogroups based on the structure of the polysaccharide capsule. Serogroups A, B, C, W, X and Y are responsible for over 95% of cases of meningococcal disease cases worldwide.

Meningococcal infection is transmitted from person to person through infectious respiratory particles and throat secretions, with both individuals with overt meningococcal disease and asymptomatic nasopharyngeal carriers serving as potential sources of infection.

Outbreaks and epidemics of meningococcal disease are more likely to occur in settings that facilitate transmission, including regions with low vaccination coverage, overcrowded living conditions, and areas with limited or disrupted access to health services (e.g. conflict-afflicted areas and refugee camps). The disease burden is particularly high in the African meningitis belt, a geographical region stretching from Senegal in the west to Ethiopia in the east, where outbreaks and epidemics are most common during the dry season (from December to June). Before the introduction of serogroup A conjugate meningococcal vaccine (MenACV) through mass preventive campaigns and in routine immunization programmes, serogroup A was the most frequent causative agent, accounting for large-scale recurrent epidemics. Since the roll-out of MenACV, serogroups C, W and X have been predominant, with seasonal epidemics generally smaller in size. In the Middle East, meningococcal disease outbreaks often occur in conflict settings or in relation to mass gatherings. In high-income countries across North America, Europe and Oceania, serogroups B, C, W and Y are responsible for sporadic cases and small-scale outbreaks, with peak incidence in later winter and early spring.

While all age groups are at risk, meningococcal infection is a leading cause of bacterial meningitis in children and young adults. Colonization of the nasopharynx is a prerequisite condition for the development of invasive disease. Additional risk factors include anatomical or functional asplenia (e.g. post-splenectomy and sickle cell disease), complement component deficiencies or inhibitors, and HIV infection.

Vaccination remains the most effective public health strategy to prevent meningococcal disease. In addition, according to the WHO guidelines on meningitis diagnosis, treatment and care (2025) antibiotic prophylaxis should be provided to close contacts of cases to prevent secondary transmission

Meningococcal vaccines

Meningococcal polysaccharide vaccines are gradually being replaced by polysaccharide-protein conjugate vaccines, which are more immunogenic and effective in preventing nasopharyngeal carriage of the bacteria and thus its transmission. They are available in monovalent (A or C), quadrivalent (A, C, W, Y), pentavalent (A, C, W, Y, X) or combination (serogroup C and Haemophilus influenzae type b) formulations. Two protein-based vaccines are now available that offer protection against serogroup B meningococcal disease – they have also recently been made available in combination with quadrivalent conjugate vaccines.

Meningococcal vaccine standardization

Written standards

Meningococcal A vaccines

The recommendations include provisions for the production and quality control of meningococcal A conjugate vaccines were adopted in 2006.

Recommendations to assure the quality, safety and efficacy of group A meningococcal conjugate vaccines, TRS 962, Annex 2

Meningococcal C vaccines

The recommendations for the production and control of meningococcal group C conjugate vaccines were updated in 2001. An addendum was developed in 2003 which included for serological assays to evaluate the immune response to meningococcal conjugate vaccines. The clinical evaluation of group C meningococcal conjugate vaccines was further updated in 2007.

Meningococcal polysaccharides vaccines (unconjugated)

WHO recommendations for meningococcal vaccines which were first adopted in 1975 described the production and quality control of A and C polysaccharide vaccine preparations. These were updated in 1980 to include provisions for the increased potency attainable through reduction in the endotoxin content, the use of lactose as a thermal stabilizer, and to include the Y, 29E, and W135 strains. Another amendment in the 1999 reduced the number of guinea pigs required for the abnormal toxicity test.


WHO reference materials for Meningococcal vaccines are available