Which type of vaccine protects against Diphtheria?

Question

UnlockIAS · Accepted Answer

Correct — A, Toxoid. Diphtheria is caused not by the bacterium itself but by the exotoxin secreted by Corynebacterium diphtheriae. The vaccine therefore uses a toxoid — the diphtheria toxin chemically inactivated (e.g., with formaldehyde) so it can no longer cause disease but still triggers protective anti-toxin antibodies. This diphtheria toxoid is combined with tetanus toxoid and pertussis antigen in the familiar DPT/DTaP vaccine.

Why the other options are wrong — (b) Live-attenuated vaccines use a weakened live pathogen (e.g., BCG, oral polio, MMR). Diphtheria protection targets the toxin, not a live organism, so a toxoid — not a live vaccine — is used.  (c) mRNA vaccines deliver messenger RNA coding for an antigen (used in some COVID-19 vaccines). This platform is not used for diphtheria, whose protection is toxin-based.  (d) Viral-vector vaccines use a harmless virus to carry antigen genes (e.g., Covishield/Sputnik V for COVID-19). This is not the platform for the diphtheria vaccine.

Concept: Vaccines are grouped by platform: live-attenuated, inactivated (killed), subunit/conjugate, toxoid, mRNA and viral-vector. A toxoid vaccine is used when the disease is caused by a bacterial exotoxin — the toxin is inactivated into a harmless 'toxoid' that still provokes anti-toxin immunity. Diphtheria and tetanus are the classic toxoid-vaccine diseases, delivered together with pertussis as DPT.

State PCS 2023 Q138 — Science & Technology PYQ with Answer

State PCS 2023 Q138 — Science & Technology PYQ with Answer