Why do vaccines fail?
By Dairy Herd news staff  |  Wednesday, May 27, 2009

Dick Wallace, University of Illinois extension dairy veterinarian, shared several reasons for vaccination failure during a heifer-management Webinar last month. “Just because you inject (a vaccine) into an animal doesn’t mean you are going to get immunization or an immune response,” he said. Here are several other reasons:

• Some virulent strains of disease may override the effectiveness of a vaccine.
• Immune suppression. If heifers have poor nutrition, for example, they don’t respond to vaccination.
• Improper vaccine use. Sometimes people use vaccines for conditions for which they were not designed.
• No booster. Giving only one dose of a killed vaccine is probably “a wasted event,” Wallace said.
• Too long of a time period between boosters.
• Maternal antibodies from colostrum. If there are enough antibodies residual in the calf’s system, it’s going to prevent a modified-live vaccine from working. However, there is new evidence that some modified-live vaccines will work in the face of maternal antibodies, Wallace said.

Remember, vaccines are not a substitute for good management. “If you don’t have good management processes in place — good ventilation, good housing, good nutrition — vaccines are really not going to have as much benefit for you as possible,” Wallace concludes.