## **Core Concept**
The cholera vaccine is used to protect against cholera, a diarrheal disease caused by *Vibrio cholerae*. The effectiveness of the vaccine is crucial in preventing outbreaks, particularly in areas with poor sanitation and during humanitarian crises. The vaccine works by inducing immunity against the cholera toxin.

## **Why the Correct Answer is Right**
The correct answer, **85-90%**, reflects the high efficacy of the current cholera vaccines, which are primarily based on the inactivated *Vibrio cholerae* O1 and sometimes O139. These vaccines provide significant protection against cholera, especially within the first year after vaccination. The protection might wane over time, necessitating booster doses.

## **Why Each Wrong Option is Incorrect**
- **Option A:** *50-60%* - This option underestimates the effectiveness of modern cholera vaccines. While earlier vaccines had lower efficacy, current vaccines have shown significantly higher protection rates.
- **Option B:** *60-70%* - Still underestimates the efficacy of the current cholera vaccines, which have demonstrated higher effectiveness in clinical trials and field studies.
- **Option D:** *95-100%* - Overestimates the effectiveness. While the vaccine is highly effective, no vaccine provides 100% protection, and there is always a small chance of breakthrough infections.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that cholera vaccines are not just for travelers but are also crucial in outbreak control and for individuals living in endemic areas. The vaccine's effectiveness wanes over time, typically requiring booster doses for sustained protection.

## **Correct Answer:** . **85-90%**