Equine Vaccines

The questions:


The Answers:

Q: Why should my horse be vaccinated?

Vaccinations protect your horse against life threatening diseases such as tetanus, and diseases that can severely affect its health and performance, such as equine influenza (flu) and herpes virus infection.

Vaccination is the only proven method of protecting against these diseases: there is no specific cure for them and treatment may be not only unsuccessful but extremely expensive.

The organism which causes tetanus, Clostridium tetani, lives in the soil, and is rife in some areas. It enters tissues through wounds, and horses are particularly susceptible. If a horse has not been immunised, it is likely to need a shot of tetanus antitoxin for even minor wounds or when it undergoes a surgical procedure. The organism thrives without oxygen: it can enter a small puncture wound, such as a nail or thorn prick, which may well go unnoticed. Even when antitoxin is given, the often fatal disease can take hold. Only vaccination provides long term protection against this happening.

The high percentage of horses within the UK which are regularly vaccinated is believed to be a major reason in reducing the numbers of large epidemics of influenza. Moreover the incidence of clinical disease during an outbreak is markedly reduced when the equine population is protected by vaccination.

These diseases, preventable by vaccination, have not been eradicated: your horse might come into contact with them. Booster vaccination is an effective way of ‘topping up’ a horse’s immunity thereby minimising the risk of disease when challenged by natural infection.

Back to top…

Q: What should it be vaccinated against?

The most common diseases to vaccinate against are tetanus and equine influenza. Other vaccines exist for herpes, rotavirus and EVA (equine viral arteritis).

Back to top…

Q: When should it be vaccinated?

Your vet will advise you on the best time, and the frequency of booster vaccinations, based on the manufacturers’ recommendations for the vaccine he or she uses. This is also based on the competition entry rules for equine governing bodies which aim to minimise the risk of infectious diseases at events where horses come into contact with each other e.g. race meetings, 3 day events.

Many competitions require proof of flu vaccination. It is a sensible precaution to vaccinate before exposing your horse or pony to any situation where it will mix with large numbers of horses from different environments. Also, the introduction of a new horse to your stable could present a potential for exposure to infection.

Back to top…

Q: I have heard vaccines can cause side effects: is this true?

Although all veterinary vaccines undergo thorough, independent evaluation of their safety, efficacy and quality, occasional reactions may occur in individual cases. This may be an injection site reaction, allergic reaction or general malaise.

If your vet thinks your horse is one of the very few that has suffered a local or overall reaction to a vaccine, there is a system called the Suspected Adverse Reaction Surveillance Scheme (SARSS), operated by the Veterinary Medicines Directorate (VMD), where reports should be made. Horse owners themselves can also make reports direct to the VMD. This scheme keeps an overall check on adverse reactions.

The results of the VMD’s SARSS scheme are published and indicate a low rate of apparent adverse reaction. In 2009 only 3 horses in total were reported to have shown any apparent reaction to vaccination.(1) It must be remembered, though, that the very small risk of a vaccine side effect is greatly outweighed by the benefit of protection against serious disease.

Under EU and UK law all horse vaccines used in the UK must be licensed for use here and be prescribed by your horse’s vet. Always avoid any temptation to by-pass this system by using foreign or otherwise illegal products.

Back to top…

Q: Does my horse need rest after vaccination?

This was frequently recommended for older vaccines, and is no longer stipulated with more modern vaccines. Nevertheless, talk to your vet, as he or she will be able to offer tailor-made advice for your particular horse and the work it is doing.

Back to top…

Q: What should I do if I think my horse develops respiratory disease following vaccination?

A number of different clinical conditions can cause horses to show signs of respiratory disease. If a horse is showing signs of respiratory disease, it is advisable to arrange for your veterinary surgeon to examine the horse.

In the past, flu vaccines in both man and animals had the reputation of not working well. Equine flu vaccines were developed in the mid 1960’s in response to the worldwide epidemic of the ‘Miami’ strain, and were not terribly effective. Things have moved on immeasurably since then. Manufacturers regularly update their ‘flu vaccines to ensure they are effective against the latest strains of ‘flu virus.

Should your veterinary surgeon suspect that your horse is showing signs of flu virus infection, even though they have been vaccinated against the disease, they should report their concerns to the manufacturer of the vaccine and/or the VMD.

Back to top…

Q: Homeopathic vaccines: what about them?

Whether for disease prevention or treatment, the veterinarian and the horse owner have a right to expect that the preparation of animal medicines is reliably based on the triple standards of quality, safety and efficacy. The extremely stringent requirements for product registration reflect this.

The main concern most vets have about the use of homeopathic ‘vaccines’ (nosodes) is that there is no proper independent evidence to show that they are effective in protecting horses.

Indeed, the few properly designed trials that have been carried out by using homeopathic nosodes have shown no evidence of protection. Without evidence of effectiveness, homeopathic nosodes may pose far greater risk to horses and their in-contacts by leaving them susceptible to disease.

Back to top…


(1) Veterinary Record (2010) 167, 118-121 F Dyer, G Diesel, S Cooles, A Tait, Suspected Adverse Reaction Surveillance Scheme, Veterinary Medicines Directorate