**Core Concept**
The protective value of a vaccine, also known as vaccine efficacy, is a measure of how well a vaccine prevents disease in a population. In this case, a vaccine with a 95% protective value means that 95% of individuals who receive the vaccine will be protected against the disease.

**Why the Correct Answer is Right**
The 95% protective value refers to the vaccine's ability to prevent disease in a controlled clinical trial. In a trial of this type, the vaccine is given to a large group of participants, and the incidence of disease is compared to a control group that did not receive the vaccine. The 95% protective value indicates that 95% of participants who received the vaccine were protected against the disease, compared to the control group. This is calculated using the formula: (1 - (number of cases in the vaccine group / number of cases in the control group)) x 100.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the protective value of a vaccine. The protective value does not refer to the percentage of individuals who will not develop a mild case of the disease.
**Option B:** This option is incorrect because it implies that the protective value is a measure of the vaccine's ability to prevent all cases of the disease, rather than the majority of cases.
**Option C:** This option is incorrect because it does not accurately describe the protective value of a vaccine. The protective value is not a measure of the percentage of individuals who will develop a severe case of the disease.

**Clinical Pearl / High-Yield Fact**
It's essential to note that vaccine efficacy can vary depending on factors such as age, underlying health conditions, and the specific disease being targeted. Additionally, vaccine efficacy is often measured in terms of preventing severe disease, rather than mild or asymptomatic cases.

**Correct Answer:** D.