Due to COVID-19, we have all become very accustomed to vaccines and what they do, and similar to human medicine, vaccines are an extremely useful tool in animal medicine.

They ensure that the majority of animals become immune to an infectious agent before the risk of a disease outbreak, thereby avoiding the risks and losses associated with animals becoming sick and unproductive.

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, eg before housing or before the breeding season.

In some instances, vaccination does not prevent infection, but decreases the severity of disease if an animal becomes infected and/or decreases shedding of infectious organisms, which happens with pneumonia vaccines, meaning less chance for pneumonia to spread to healthy animals.

Two vaccine types exist. The first type are called inactivated vaccines (also known as killed or dead vaccines). These contain a tiny part of the disease organism, which is dead. Live vaccines are the second type of vaccine and they contain the live organism that is closely related to the disease-causing agent. This is either a non-harmful strain, or a strain that has been weakened so that it can no longer cause disease.

When a vaccine is given to an animal, it kickstarts its immune system to produce antibodies. These antibodies help the animal’s immune system recognise the infectious agent if/when the animal is exposed to it.

So, once an animal is vaccinated, if it comes into contact with the infectious agent, the immune system responds and provides sufficient protection so that the animal does not develop clinical signs.

Similar to most of the COVID-19 vaccines, many animal vaccines require a course of two doses at recommended intervals (check the label for the exact time between doses) before protection is complete, eg clostridial vaccines that protect against diseases like black leg and tetanus.

Animals are not fully protected until they have received two doses of the vaccine. However, some vaccines may be used in the face of a disease outbreak to decrease the severity of clinical signs – for example, if there is an outbreak of IBR, a live IBR marker vaccine can be given intranasally.

While some vaccines are licensed to be used together, 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 for your herd.

Vaccine storage and administration

It is important to ensure that animals are adequately restrained when vaccinating and that the proper dose is hygienically given via the correct route and according to the manufacturer’s directions. Check for any contraindications, withdrawal periods, or warnings on the package insert before you begin.

  • The importance of storing vaccines correctly and observing the expiry date cannot be overemphasised, as vaccine effectiveness may be reduced by poor storage or inappropriate administration.
  • Most vaccines need to be protected from sunlight and refrigerated, usually between 2-8°C, but freezing may destroy them. Once again, check the label.
  • Live vaccines may come as two vials, one liquid and one powder, which must be mixed before use. See the package insert on how to mix the vaccine and remember, vaccines are only effective for a few hours once opened or mixed. Dispose of the remaining unused vaccine to avoid the temptation to use it at a later date.
  • Most cattle vaccines are administered either by injection (intramuscular or subcutaneous) or intranasally. Where possible, use an automatic vaccinator that is correctly calibrated to avoid contaminating the bottle of vaccine. If this is not an option, have one sterile needle that remains in the vaccine bottle and have a different needle for injecting the animal, replacing it regularly to avoid it becoming blunt.
  • Although very rare, vaccination carries the risk of adverse reactions, ranging from mild injection site reactions to severe anaphylactic (shock) reactions. Therefore, it is important to monitor animals following vaccination for signs of unexpected changes in behaviour. Reassuringly, regulatory authorities and vaccine companies ensure that rigorous standards are applied to ensure vaccines are of consistent quality, safety and efficacy.
  • Good records are key

    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 helpful information when assessing your herd health programme annually, even if your herd health planning is an informal chat with your veterinary practitioner during the annual TB test. Finally, records provide valuable information, should ‘vaccine failure’ be suspected. 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. Vaccines work best when animals are healthy and not under stress, as stress can temporarily decrease the animal’s immune response, potentially affecting vaccine efficacy.

    Herdowners should contact their veterinary practitioner to discuss which vaccines they should incorporate into their herd health plan. Each herd is unique and may be exposed to different disease risks, so 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.