Cow-Calf Certification Practice Exam

What environmental factor can reduce the efficacy of modified live virus vaccines?

1. Keeping vaccines cold

2. Using a new needle

3. Leaving the vaccines out in the light

4. Storing in a dark place

The correct answer is: Leaving the vaccines out in the light

Leaving vaccines out in the light can significantly reduce the efficacy of modified live virus vaccines. This is primarily because exposure to light, especially ultraviolet light, can cause the virus particles in the vaccine to become unstable or degrade. Modified live virus vaccines must maintain their integrity to effectively stimulate an immune response in the animal. When light exposure occurs, it can break down the viral components, rendering the vaccine less effective or even ineffective. In contrast, keeping vaccines cold is essential for maintaining their effectiveness, and storing them in a dark place protects them from light exposure. Utilizing a new needle is a good practice for preventing contamination during administration but does not directly impact the viability of the vaccine itself. Thus, the correct choice highlights a crucial aspect of vaccine storage and handling—protecting vaccines from light exposure to ensure their effectiveness.