## Core Concept
The question tests knowledge of vaccines and their usage across different age groups, particularly focusing on vaccines that have specific age restrictions or recommendations.

## Why the Correct Answer is Right
The correct answer, **BCG (Bacillus Calmette-Guérin) vaccine**, is primarily used against tuberculosis. It is a live attenuated vaccine and is generally administered to infants in countries with high prevalence of TB or as part of a vaccination program. The BCG vaccine is not routinely recommended for adults in many countries due to its variable efficacy in adults and the low risk of severe TB in this age group. However, it might be recommended for certain high-risk adults.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is not provided, but typically vaccines like Hepatitis A, Hepatitis B, and others can be used in adults.
- **Option B:** This option is not provided, but many vaccines are indeed used in adults, such as Influenza, Pneumococcal, and COVID-19 vaccines.
- **Option C:** This option is not provided, but similar to option B, many vaccines are indicated for adult populations.
- **Option D:** This option is not provided but presumably another vaccine that can be used in adults.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the **BCG vaccine** is primarily for infants and certain high-risk groups, not routinely for all adults. This is an important consideration in vaccine administration to avoid unnecessary exposure to live vaccines in populations where the risk-benefit ratio is not favorable.

## Correct Answer: B. BCG vaccine