A 2-year-old child diagnosed provisionally with diphtheria and on examination she has greyish white membrane patch around her tonsils. The child has a 6-year-old sibling at home, who is fully immunized as per the schedule. What is the best measure to prevent disease in the sibling of the child

**Core Concept**
The underlying principle being tested involves **diphtheria**, a serious bacterial infection caused by *Corynebacterium diphtheriae*, and measures to prevent its spread. **Immunization** plays a crucial role in preventing diphtheria.

**Why the Correct Answer is Right**
Since the correct answer is not provided, I will discuss the general approach to preventing diphtheria in contacts. The best measure to prevent the disease in the sibling would involve ensuring the sibling's **immunization status** is up-to-date, as diphtheria toxoid is part of routine childhood vaccinations.

**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific option, it's challenging to provide a detailed explanation, but typically, incorrect options might include measures that are not evidence-based or not specifically targeted at preventing diphtheria.
**Option B:** Similarly, without details, this option might be incorrect if it suggests a measure that does not align with preventing diphtheria transmission, such as inadequate isolation or inappropriate use of antibiotics.
**Option C:** This option could be incorrect if it proposes a method that is not recommended for diphtheria prevention, such as an unnecessary or inappropriate vaccine booster.
**Option D:** This might be incorrect if it suggests no action is needed, ignoring the potential risk to the sibling.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **diphtheria toxoid** is highly effective in preventing the disease, and ensuring all contacts are up-to-date with their vaccinations is crucial in managing outbreaks.

**Correct Answer:** Unfortunately, without the answer choices, I cannot provide the correct answer line.

✓ Correct Answer: C. Nothing is required to be done