According to AHI’s (Animal Health Ireland), Michelle McGrath, vaccines are “an extremely useful tool” to ensure most animals become immune to an infectious agent before the risk of a disease outbreak.
Vaccines take time to provide a sufficient protective cover, so ideally, farmers should plan to use them well in advance of when their animals need protection.
In some instances, farmers should note that vaccination does not prevent infection but decreases the severity of clinical disease if an animal becomes infected and/or decreases shedding of infectious organisms.
Inactivated & live vaccines
Two vaccine types exist: inactivated and live vaccines:
- Inactivated vaccines (also known as killed or dead vaccines) contain the disease organism or a toxin produced by the organism that has been inactivated during product manufacture;
- Live vaccines contain a live organism that is closely related to the disease-causing agent. It is either a non-harmful strain or a strain that has been weakened or modified so that it can no longer cause disease.
When a vaccine is given to an animal, it stimulates the animal’s immune system leading to the production of special proteins called antibodies.
These antibodies, she explains, help the animal’s immune system recognise the infectious agent if or when the animal is exposed to it.
She says: “So once an animal is vaccinated, if the animal comes into contact with the infectious agent, the immune system responds and provides sufficient protection so that the animal develops reduced or no clinical signs and poses less of a risk for spread of infection within the herd.”
“Many vaccines (particularly inactivated ones) require a primary course of two doses at recommended intervals (check the label for the exact interval) before protection is complete e.g. clostridial vaccines and animals are not fully protected until they have received the two doses.”
“However, some vaccines may be used in the face of a disease outbreak to decrease the severity of clinical signs, e.g. live IBR marker vaccines given intranasally.”
While some vaccines are licenced to be given at the same time, in general, giving multiple vaccines at one time should be discussed with your veterinary practitioner on a case-by-case basis to determine whether this is appropriate, she advises.
Recording details of vaccine use is extremely important for several reasons.
Firstly, it will ensure booster doses are given at the correct time. It also provides useful information when assessing your herd health programme annually.
Finally, records provide “valuable” information should a ‘vaccine breakdown’ be suspected.
She adds: “Remember that even the most efficient vaccines are not 100% effective in preventing disease.”
“Vaccines depend on the animal’s immune response to ensure good protection against a particular disease.”
“In any group of animals, a small number of individuals may fail to respond to vaccination as a result of a reduced immune response.”
“A satisfactory immune response will only be achieved when animals are healthy and not under stress as this can temporarily decrease the animal’s immune response, potentially affecting vaccine efficacy.”
Herdowners should contact their vet to discuss which vaccines they should incorporate into their herd health plan.
Each herd is unique and may be exposed to different disease risks.
Therefore, it is essential to develop a vaccination plan that suits your herd and use vaccines strategically.
It is important to remember that vaccination is only one part of disease prevention and cannot compensate for poor management or insufficient attention to biosecurity.
If some diseases have historically been a problem on your farm, review these with your veterinary surgeon.
For example, if calf scour is a problem on your farm discuss the likely causes and what can be done to prevent it.
This may involve vaccinating the cow at least three weeks before her due date.
“Vaccination is one tool used to manage calf scours and not a silver bullet,” she stresses.
“If other management procedures are not in place, such as hygiene, housing, colostrum management, then you will have poor success in controlling calf scour through a dam vaccination programme.”
A calf is born without antibodies and depends on their absorption from colostrum (first milk after calving) to gain immunity until they develop their own immunity at 3 to 4 weeks of age.
The ability of the calf to absorb antibodies decreases every hour from birth (read about ‘the golden hour’ in this news article) and stops when the calf is 24-hours-old.
The simple rule is to:
- Use colostrum from the first milking for the first feed;
- Give colostrum within two hours from the calf’s birth;
- Give at least three litres.
Read this article on 30 key messages for calf rearers from Tommy the Vet.