**Core Concept**
The concept of specific protection by vaccines refers to the ability of a vaccine to provide immunity against a specific disease by inducing a targeted immune response. This concept is crucial in the development and implementation of vaccines to prevent infectious diseases.

**Why the Correct Answer is Right**
The correct answer is Louis Pasteur, who is considered the pioneer in the concept of specific protection by vaccines. Pasteur developed the first vaccines for anthrax and rabies, demonstrating the efficacy of vaccines in preventing disease. His work laid the foundation for modern vaccine development and the understanding of specific immunity. Pasteur's vaccines worked by introducing a small, harmless piece of a pathogen, such as a virus or bacterium, to the body, which then mounts a targeted immune response to attack the pathogen if it enters the body in the future.

**Why Each Wrong Option is Incorrect**
**Option A:** Edward Jenner, who developed the first vaccine for smallpox, is often credited with the development of vaccines, but he built upon Pasteur's work and understanding of specific protection.
**Option B:** Robert Koch, a German microbiologist, made significant contributions to the field of microbiology and the development of vaccines, but he is not considered the pioneer in the concept of specific protection by vaccines.
**Option C:** Louis Pasteur's work on vaccines was groundbreaking, but he is not the only pioneer in the field, and other scientists, such as Edward Jenner, also made significant contributions.

**Clinical Pearl / High-Yield Fact**
The concept of specific protection by vaccines relies on the development of a targeted immune response, which can be achieved by introducing a small, harmless piece of a pathogen to the body. This understanding is crucial in the development of modern vaccines and the prevention of infectious diseases.

**Correct Answer:** C. Louis Pasteur