Why vaccination remains an important part of herd health protection

Infectious diseases are a major cause of concern in both human and veterinary medicine. Both the Covid-19 pandemic in human populations worldwide and the recent EHV-1 (Equine Herpes Virus – 1) neurological outbreak which originated in Valencia, Spain February 2021 have dramatically demonstrated that the introduction of an infectious agent into a susceptible population can have devastating consequences.

The purpose of a vaccine is to stimulate a protective immune response that either prevents infection or limits seriousness of disease. Vaccination involves the administration of the causative organisms or important components of those organisms that initiate an immune response.

Vaccines are most effective if enough individuals in a population are vaccinated to achieve herd immunity. Herd immunity is the theory that when a high proportion of individuals in a population develops immunity against an infectious disease after previous infection or vaccination, the spread of that disease slows. An objective of vaccination programmes is to prevent disease outbreaks so everyone benefits, including those that respond poorly to vaccination.

Vaccines are available against Influenza, Tetanus, Strangles, Equine Herpes Virus, Rotavirus, Equine Infectious Anaemia (EIA) and in other countries and continents additional vaccines against Rabies, West Nile Virus, and other agents are in use. Whether a vaccine is recommended or not may depend on the likelihood of exposure to the particular disease, determined by environment, age, breed, sex and use.

After the immunisation procedure is completed, the protective antibodies in the blood and specialised immune system components stand guard against the invasion of specific diseases. However, these antibodies gradually decline. Therefore, a booster is needed at regular intervals to maintain adequate protection. Protection against some diseases, such as tetanus can be accomplished by boosters once a year while others require more frequent intervals to provide adequate protection.

There is no such thing as a perfect vaccine, but overall vaccination is far less costly and stressful than infection. Sometimes an individual develops a reaction to a vaccine, such as heat and swelling at the site of vaccination—this is a sign that the body’s immune system has been provoked into action. Major adverse reactions are, thankfully, relatively uncommon.

A good immunisation program is essential to responsible equine ownership, but just as in people, vaccination does not guarantee 100% protection.

1. Vaccination serves to minimise the risk of infection, but does not prevent disease in all circumstances.
2. A primary series of vaccines and booster doses should be administered before likely exposure.
3. Each equine in a population is not protected to an equal degree or for an equal duration following vaccination.
4. All equines in a yard should be vaccinated and if possible the same schedule should be

It could be suggested that complacency has arisen about what can be achieved by vaccination. Many are unaware of the devastating impact childhood diseases had before routine immunisation became available. Unfortunately, vaccine-preventable diseases are on the increase due to vaccine hesitancy in both human and animal populations. Equine vaccines are protective in most cases, with very little downside to their use.

By exercising equines regularly and building up strength in their muscles and bone, they can perform athletically at an optimal level. The same is true for the immune system. By ‘exercising’ the immune system through the routine use of vaccination, this allows equines to optimally resist the infectious disease agents they may encounter.

Have a conversation with your vet about the risk level of the equines on your enterprise and the recommended vaccination programme.