**Core Concept**
The question is testing the understanding of live attenuated vaccines and their contraindications in immunocompromised individuals. The BCG vaccine is a live attenuated vaccine used to protect against tuberculosis, which raises concerns in patients with compromised immune systems.

**Why the Correct Answer is Right**
The BCG vaccine is a live attenuated vaccine, meaning it contains a weakened form of the Mycobacterium bovis bacteria. In immunocompromised individuals, such as those with chronic infections or compromised immune function, live attenuated vaccines can cause disease rather than providing protection. This is because their immune system is unable to mount a sufficient response to the vaccine, leading to uncontrolled replication of the vaccine strain. In the case of the young girl with repeated infections, her immune system is likely compromised, making the BCG vaccine contraindicated.

**Why Each Wrong Option is Incorrect**
**Option A:** Inactivated polio vaccine (IPV) and diphtheria toxoid are both inactivated vaccines, which are generally safe for use in immunocompromised individuals. In contrast, live attenuated vaccines like BCG are contraindicated.
**Option B:** The Bordetella pertussis vaccine is a component of the whole-cell pertussis vaccine, which is inactivated. As mentioned earlier, inactivated vaccines are safe for use in immunocompromised individuals.
**Option C:** Diphtheria toxoid is an inactivated toxin, which is also safe for use in immunocompromised individuals.

**Clinical Pearl / High-Yield Fact**
Immunocompromised individuals should be cautious with live attenuated vaccines, as they can cause disease rather than providing protection. Always check the vaccine type and the patient's immune status before administering any vaccine.

**✓ Correct Answer: A. Bacillus Calmette-Guerin (BCG)**