Basic Principles of Vaccine Use

6.5.1 Basic Principles of Vaccine Use Many types of vaccines provide immunity of varying duration against different diseases. Always follow the instructions and heed the precautions provided with the vaccine. Remember the following general principles:

1. Vaccines should be obtained from a reputable source. Poor quality vaccines can kill and mishandled vaccines can lose their effectiveness. When vaccines cause damage or are not effective, farmers lose confidence in both the AHA and the vaccine.

2. A vaccine is used to prevent disease, not to treat it. Once the animal is sick, it is too late to vaccinate it against that disease. Vaccinating sick animals seldom produces immunity and may make the disease worse.

3. In general, do not vaccinate sick animals.

4. Follow the manufacturer's instructions about vaccinating pregnant animals since some vaccines can cause abortion.

5. Most vaccines provide protection one to two weeks after the vaccine is given. If the animal already has the organism in its body when the vaccine is given, or if the animal is exposed to the organism within one or two weeks after vaccination, it may still become ill. Some vaccines require two injections given three to four weeks apart to provide good protection. The animal is therefore not protected until a few weeks after the second vaccination. The AHA must carefully explain this to livestock owners to avoid being blamed if the animal becomes ill before it is protected by the vaccine.