Which type of vaccine protects against diphtheria?

1. A

   Toxoid

   Option (a) claims that a toxoid vaccine is used to protect against diphtheria. This is the correct official key because the diphtheria vaccine, usually administered as DTP or DTaP, contains an inactivated bacterial toxin, known as a toxoid, to stimulate immunity against the disease-causing exotoxin produced by Corynebacterium diphtheriae rather than the live bacterium itself.

2. B

   Live-attenuated

   Option (b) claims that a live-attenuated vaccine is used against diphtheria. This is incorrect because live-attenuated vaccines contain weakened forms of living pathogens, whereas bacterial diseases like diphtheria and tetanus rely on toxoid-based immunizations instead.

3. C

   mRNA

   Option (c) claims that an mRNA vaccine protects against diphtheria. This is incorrect because mRNA technology instructs cells to produce a protein piece to trigger an immune response, which is not the standard or historical methodology utilized for standard bacterial toxoid vaccines.

4. D

   Viral vector

   Option (d) claims that a viral vector vaccine is used for diphtheria. This is incorrect as viral vector platforms use a modified, harmless virus to deliver genetic material, which does not match the toxoid composition required to neutralize bacterial exotoxins.

Summary. Official key is (a) Toxoid. Diphtheria is a serious bacterial infection caused by Corynebacterium diphtheriae, which primarily affects the mucous membranes of the nose and throat. Because the dangerous symptoms are caused by the exotoxin released by the bacteria, medical science utilizes inactivated toxins called toxoids to safely provoke an immune response. Options (b), (c), and (d) suggest alternative vaccine platforms like live-attenuated, mRNA, and viral vector types, which are not the traditional mechanism for diphtheria prevention. Therefore, only option (a) correctly identifies the toxoid vaccine classification.