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• MCV4 (Menactra^®) is a sterile suspension containing purified capsular polysaccharide antigens A, C, Y, and W-135 extracted from N. meningitidis and conjugated to diphtheria toxoid protein.
• MPSV4 (Menomune^®) is a lyophilized preparation containing purified capsular polysaccharide antigens A, C, Y, and W-135 isolated from N. meningitidis. The antigens are unconjugated.
• Meningococcal vaccines stimulate active immunity to meningococcal infection by inducing production of specific IgG, IgM, and IgA antibodies. The relative importance of each type of antibody in providing initial and long-term bactericidal protection against N. meningitidis has not been determined.
• The antigens contained in MPSV4 (Menomune^®) cannot induce long-lasting immunity or an anamnestic response after subsequent exposure to the same antigens since polysaccharide antigens alone are T-cell independent.
• Because the antigens contained in MCV4 (Menactra^®) are conjugated to diphtheria toxoid, a protein carrier containing T-cell epitopes, the vaccine can elicit an immune response involving T-cells and may provide longer-lasting immunity than that provided by the unconjugated vaccine.
• Extent and duration of the immunologic response to MPSV4 (Menomune^®) vary depending on the age of the recipient; the vaccine is less immunogenic in children <2 years of age than in older children and adults. Anticapsular antibodies following vaccination with MPSV4 (Menomune^®) generally appear in serum within 7 days and peak within 14 days.
• Data are limited to date regarding the immunologic response to MCV4 (Menactra^®), but there is evidence that the conjugated meningococcal vaccine is at least as immunogenic as the unconjugated meningococcal vaccine (MPSV4, Menomune^®) in individuals 11–55 years of age. Additional study and long-term follow-up are necessary to fully evaluate the immunogenicity of MCV4 (Menactra^®) and to determine the duration of protection.
• Protective antibody levels may be achieved within 7–10 days after a dose of MCV4 (Menactra^®) or MPSV4 (Menomune^®).
• A reduced immune response to meningococcal vaccines and lower antibody titers may occur in immunocompromised individuals (e.g., HIV-infected individuals, those with leukemia, lymphoma, or generalized malignancy, those receiving immunosuppressive therapy).
• The principal mode of transmission of meningococcal infection is respiratory, most commonly through close personal contact with an individual with invasive meningococcal disease or direct exposure to nasopharyngeal secretions from an infected individual. However, the vast majority of cases of meningococcal disease in the US occur in individuals who have had no known exposure and presumably acquire infection from an asymptomatic carrier. Invasive infection with N. meningitidis usually results in meningitis and/or meningococcemia. Onset of illness is usually sudden with signs and symptoms including fever, severe headache, stiff neck, nausea, vomiting, and rash. Invasive meningococcal disease occurs most frequently in children <5 years of age and in adolescents 15–18 years of age.
• The minimum titer of anticapsular antibodies conferring protection against N. meningitidis serogroups A, C, Y, and W-135 has not been established; however, studies evaluating serogroup A and C meningococcal disease indicate that anticapsular antibody levels of ≥2 mcg/mL may be protective. Seroconversion usually is defined as ≥2-fold increase in serum anticapsular antibody titers or a ≥4-fold increase in bactericidal antibody titers.