Question:
The vaccine against Neisseria meningitidis contains which of the following?
The vaccine against Neisseria meningitidis contains which of the following?
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The serogroup-defining outer layer of the meningococcus is the vaccine antigen.
Updated On: Jun 24, 2026
- Whole bacteria
- Capsular polysaccharide
- Somatic 'O' antigen
- None of these
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The Correct Option is B
Solution and Explanation
Step 1: Meningococcal vaccines are designed to prevent infection by Neisseria meningitidis. The protective antigen of this organism is its outer polysaccharide capsule, which also defines the serogroups (A, B, C, W-135, Y).
Step 2: The classic vaccines are prepared from purified capsular polysaccharides of groups A, C, Y and W-135. They can be bivalent (A and C) or tetravalent (A, C, Y, W-135), and the immunity produced is group-specific.
Step 3: Therefore the correct answer is capsular polysaccharide. Whole bacteria are not used, and somatic 'O' antigen is a feature of Gram negative enteric bacteria like Salmonella, not the basis of the meningococcal vaccine. Note that group B is poorly immunogenic as a plain polysaccharide, which is why a separate protein-based approach is needed for it.
Step 2: The classic vaccines are prepared from purified capsular polysaccharides of groups A, C, Y and W-135. They can be bivalent (A and C) or tetravalent (A, C, Y, W-135), and the immunity produced is group-specific.
Step 3: Therefore the correct answer is capsular polysaccharide. Whole bacteria are not used, and somatic 'O' antigen is a feature of Gram negative enteric bacteria like Salmonella, not the basis of the meningococcal vaccine. Note that group B is poorly immunogenic as a plain polysaccharide, which is why a separate protein-based approach is needed for it.
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