**Core Concept**
Primary prevention involves measures taken to prevent the occurrence of a disease or injury in the first place. This includes interventions aimed at reducing the risk factors or hazards that may lead to the disease, such as vaccination, health education, and environmental modifications.

**Why the Correct Answer is Right**
The correct answer is one of the options listed below. Primary prevention typically involves measures that are proactive and aimed at preventing the disease before it occurs. This can include vaccinations, which are a common example of primary prevention. Vaccinations work by introducing a small, harmless piece of a pathogen to the body, which stimulates the immune system to produce antibodies that can recognize and fight the pathogen in the future.

**Why Each Wrong Option is Incorrect**

**Option A:** Vaccination is an example of primary prevention, as it aims to prevent the occurrence of a disease by introducing a harmless piece of the pathogen to the body.
**Option B:** Health education is also an example of primary prevention, as it aims to educate individuals about healthy behaviors and lifestyles that can reduce the risk of disease.
**Option C:** Screening tests, such as mammograms or colonoscopies, are an example of secondary prevention, as they aim to detect disease early, when it is more treatable.

**Clinical Pearl / High-Yield Fact**
Remember that primary prevention is all about preventing disease before it occurs, whereas secondary prevention is about detecting disease early, and tertiary prevention is about managing disease after it has occurred.

**Correct Answer:** C. Screening tests are an example of secondary prevention, not primary prevention.