Editorial. Meningococcal Disease has International Public Health Impact
Published: 16.08.12 Updated: 16.08.2012 10:10:49
K. Kutsar, Editor-in-Chief
Citation: Kutsar K. Meningococcal disease has international public health impact. EpiNorth 2012; 13: 3-4
Meningococcal disease has still important public health impact in the countries of EpiNorth project activities. This is the reason why these countries should keep updated the surveillance systems to characterize meningococcal disease epidemiology, including a standard clinical case and laboratory diagnostics definitions, field investigation of cases and outbreaks, and laboratory capacity for the confirmation and characterization of the etiological agents. Continued surveillance of invasive meningococcal disease should indicate the need and timing of meningococcal vaccination.
In most countries, Neisseria meningitidis is recognized as a leading cause of meningitis and fulminant septicaemia and a significant public health problem. Invasive meningococcal infections are caused by the serogroup A, B, C, X, W135 or Y meningococci. They have the potential to cause both endemic disease and outbreaks, but their prevalence varies with time and geographic location. In Europe, the incidence of meningococcal disease ranges from 0.2 to 14 cases per 100,000 population and the majority of cases are caused by serogroup B strains. WHO definitions of a meningococcal endemic (endemicity) are incidences of >10 cases (high), 2-10 cases (moderate), and <2 cases (low) per 100 000 population. Most countries in EpiNorth project region are meningococcal disease low endemicity countries according to 2010 incidence data (Belarus 1.4, Denmark 1.3, Estonia 0.1, Finland 0.6, Latvia 0.4, Lithuania 1.5, Norway 0.8, Poland 0.6, Sweden 0.7, Ukraine 1.1, Arkhangelsk oblast 1.6, Leningrad oblast 1.3, Pskov oblast 1.7, Vologda oblast 0.7, Republic of Karelia 1.5, Republic of Komi 1.8, St. Petersburg 1.5 per 100 000 population) and only Kaliningrad oblast (2.2), Murmansk oblast (4.3) and Novgorod oblast (2.5) are moderate endemicity regions.
Meningococci usually reside asymptomatically in the human nasopharynx – nasopharyngeal carriage of potentially pathogenic Neisseria meningitidis is known in 4%-35% of healthy adults. High carriage rates could develop in relatively confined populations such as army recruits and college students. Bactericidal antibodies develop in response to nasopharyngeal carriage of meningococci and >10-14 days after nasopharyngeal colonization, development of meningococcal disease becomes unlikely. The antibody response to carriage is not limited to the strain that is being carried, but can extent to heterologous strains of pathogenic meningococci with subsequent development of specific IgG, IgM and IgA antibodies. It is not known whether nasopharyngeal carriage leads to immunological memory. Although specific antibodies are generally protective, this immunity is not absolute; meningococcal disease can occur in persons with pre-existing antibody titres.
Available meningococcal vaccines include polysaccharide vaccines and polysaccharide-protein conjugate vaccines. Polysaccharide vaccines are administered as a single dose to persons ≥2 years old. The immunogenicity and clinical efficacy of serogroup A vaccines is 85%-100%. Serogroup C vaccine is poorly immunogenic, serogroup W135 and Y vaccines are immunogenic in children aged >2 years and adults. Polysaccharide vaccines provide immunologic protection for at least three years. Conjugate vaccines are licensed for children aged >2 months, adolescents and adults. These vaccines are highly immunogenic with short-term efficacy of 92%-97% and with efficacy of 80%-85% within three to four years after vaccination. The development of vaccines against serogroup B disease has been challenging because the native B polysaccharide contains epitopes that potentially cross-react with human antigens, and is poorly immunogenic, but the newest developments are promising.
WHO recommends that countries with high or intermediate endemicity of invasive meningococcal disease and with frequent epidemics should introduce meningococcal vaccination into routine immunization programmes. In countries with low endemicity, meningococcal vaccination is recommended for defined risk groups (children and young adults residing in closed communities, laboratory workers, individuals with immunodeficiency and travellers to high-endemic areas).