A detailed discussion of meningococcal disease vaccination travel requirements and recommendations is presented in the article Alectinib datasheet by R. Steffen in this supplement. The incidence and distribution of the Neisseria meningitidis bacteria serogroups that cause the majority of invasive meningococcal disease—A, B, C, W-135, and Y—vary widely from region to region and country to country and change over time.6,10 The change in distribution of disease-causing N meningitidis serogroups, even over relatively

short periods of time, is quite unpredictable. In Europe, serogroups B and C cause the majority of disease; in Africa, serogroup A is predominant, along with C and W-135; and, in recent years, a growing proportion of meningococcal disease in the United States is attributable to serogroup Y.1,6,11 A meningococcal vaccine that provides broad protection against multiple serogroups is required to ensure the highest level of protection against meningococcal disease for travelers. Currently available vaccines to protect against meningococcal disease consist

of two major classes, quadrivalent unconjugated polysaccharide vaccines (MPSV4) and quadrivalent polysaccharide-protein conjugate vaccines Selleck BI6727 (MCV4). Although both types of vaccines provide protection against four serogroups, conjugate vaccines for meningococcal disease have several advantages over polysaccharide vaccines (Table 1).10 Polysaccharide vaccines are safe and have good short-term immunogenicity in older children and adults.6 However, polysaccharide vaccines also have several limitations in terms of duration and wide applicability.

Polysaccharide vaccines are known to have AMP deaminase poor immunogenicity and lack of effectiveness in children less than 2 years of age.10 Their mechanism of action involves a T cell-independent response; therefore, they do not induce immunologic memory. There exists the potential to induce hyporesponsiveness with repeated doses, protection is of limited duration, usually 3 to 5 years, and they show little or no protection against nasopharyngeal carriage.6,10 In contrast, the immune response to a conjugate meningococcal vaccine is T cell dependent, potentially increasing antibody levels and serum bactericidal activity (SBA) in all age groups, as well as inducing the formation of memory B cells. This population of long-lasting B cells allows the body to mount an anamnestic response after antigen reexposure.12 This provides a booster effect on subsequent vaccination or exposure and overcomes hyporesponsiveness. In addition, unlike polysaccharide meningococcal vaccines, conjugate vaccines have been shown to reduce nasopharyngeal carriage of N meningitidis and, therefore, to reduce disease transmission and contribute to herd immunity in populations.