**Core Concept**
Tetanus vaccine is a type of inactivated vaccine that provides immunity against tetanus, a bacterial infection caused by Clostridium tetani. The vaccine works by inducing the production of tetanus toxin-neutralizing antibodies. Booster doses are necessary to maintain immunity, as the protection conferred by the vaccine wanes over time.

**Why the Correct Answer is Right**
Three doses of tetanus vaccine are typically administered to provide long-term immunity against tetanus. The first dose provides initial immunity, while subsequent doses (booster shots) maintain and boost the level of antibodies against tetanus toxin. This is essential for protecting against tetanus infection, particularly in individuals who have not been previously vaccinated or whose immunity has waned. The booster doses stimulate the production of memory B cells, which quickly produce antibodies in response to tetanus toxin exposure.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the duration of immunity conferred by a single dose of tetanus vaccine is not sufficient to provide long-term protection against tetanus.
**Option B:** This option is incorrect because the number of doses required to provide immunity against tetanus varies depending on the individual's immune status and risk factors, but three doses are generally recommended for long-term protection.
**Option C:** This option is incorrect because the tetanus vaccine does not provide immunity against other bacterial infections, such as diphtheria or pertussis.

**Clinical Pearl / High-Yield Fact**
It's essential to note that tetanus immunity wanes over time, and booster shots are necessary to maintain protection. The Centers for Disease Control and Prevention (CDC) recommend a tetanus booster every 10 years for individuals who have completed the primary vaccination series.

**Correct Answer: D. Five years.**