Sometimes vaccines appear to fail to protect animals from disease. But often it's not the fault of the product. Make sure you're giving the vaccine every possible chance to work. According to Fred
Hopkins, professor in the department of animal clinical sciences at the University of Tennessee-Knox-ville, there are several common reasons for vaccine failures.

One common reason is that a booster vaccination was not given as indicated on the label. Many vaccines require two injections, often three weeks apart, to be effective. The first vaccination is a priming vaccination that activates the immune system. The second injection is actually the immunizing vaccination. Both need to be given.

A second cause of perceived vaccine failure is due to the animal's exposure to the disease too soon after the vaccine was given. Peak immunity occurs approximately three weeks after vaccination. Improper handling of the vaccine can cause many of the problems with immunity. All vaccines should be refrigerated and kept out of direct sunlight and warmer temperatures. Always follow label directions on injection type and placement.