**Question:** Drug of choice for prophylaxis of diphtheria is:

A. Penicillin
B. Tetanus Toxoid
C. Cholera Vaccine
D. Polio Vaccine

**Correct Answer: B. Tetanus Toxoid**

**Core Concept:** Tetanus is a life-threatening bacterial infection caused by the bacterium Clostridium tetani. Tetanus prophylaxis involves the administration of tetanus toxoid, which is a non-toxigenic, inactivated form of tetanus toxin. This immunizes the individual against tetanus infection by stimulating the immune system to produce neutralizing antibodies against the toxin.

**Why the Correct Answer is Right:** Tetanus toxoid is the preferred choice for prophylaxis of diphtheria because:

1. It offers long-lasting immunity: Tetanus toxoid vaccinations provide immunity for several years, ensuring protection over an extended period.
2. It is safer than tetanus toxin: Tetanus toxoid is a non-toxigenic form of the toxin, which reduces the risk of adverse reactions typically associated with using the toxin itself.
3. It is part of the routine childhood immunization schedule: Tetanus toxoid is included in the standard immunization schedule for infants and children, ensuring widespread and consistent protection across populations.

**Why Each Wrong Option is Incorrect:**

A. Penicillin: Penicillin is an antibiotic used for treating bacterial infections, including tetanus. However, it is not a prophylactic measure against tetanus.
B. Cholera Vaccine: Cholera vaccine is used for preventing cholera infection, not tetanus prophylaxis.
C. Polio Vaccine: Polio vaccine is used for preventing poliomyelitis, not tetanus prophylaxis.
D. Polio Vaccine: Similar to option C, polio vaccine is used for preventing poliomyelitis, not tetanus prophylaxis.

**Clinical Pearl:** Tetanus toxoid is an integral part of the Expanded Programme on Immunization (EPI) administered to children globally. The EPI schedule ensures that a child is protected against a range of infections, including tetanus, from birth until the age of 15-24 months, depending on the region and vaccination policies. Regular booster doses are recommended to maintain immunity as immunity wanes over time. This practice is crucial in areas with high tetanus incidence and contributes to reducing the global burden of tetanus.