Vaccines should be used as a management tool that is part of an overall program to produce a quality product. Remember that there will always be more diseases than vaccines. Vaccine use can never be expected to control all diseases or any disease in all circumstances. These vaccines can be expected to be safe and effective if properly used. Remember that no vaccine can be expected to protect perfectly, but will reduce the frequency and severity of disease.
Vaccines sometime appear to fail to protect from disease.
Usually, this is not a failure of the vaccine but due to other factors. Excess stress may suppress the immune system and hamper the response to vaccines. The vaccine was given before passive immunity from colostrum is gone. Passive immunity lasts for 3-8 months after birth. The organism causing disease may be somewhat different from herd to herd.