Vaccination plays an essential role in helping to prevent disease in our horse population. In the UK, we vaccinate horses against a number of diseases, many of which can be fatal or debilitating. Routine core vaccinations protect against equine influenza and tetanus. Other vaccines, such as EHV and Strangles, may be given according to your horse’s risk profile, but these are less common and the risks and benefits should be discussed with your vet.

How do vaccines work?

Vaccines are designed to teach your horse’s immune system how to fight a particular disease by fooling it into believing that it is being attacked by the organism causing that disease, inducing the production of protective antibodies and stimulating other immune mechanisms.

Usually, we will give your horse a primary course of injections followed by regular boosters, the frequency of which depends on the type of vaccine and the duration of immunity induced.

A ‘naive’ or unvaccinated horse exposed to a new disease is vulnerable to infection. For example, almost 100% of naive horses exposed to the flu virus will develop symptoms of the disease. Furthermore, flu is an adaptive virus that changes its character over time. Vaccine manufacturers routinely update their products to protect against new and emerging strains.

Are vaccines safe?

Decisions about vaccination should be the result of careful assessment of the risks and benefits to your animal. Although all interventions carry some degree of risk of an adverse reaction, in the case of the core flu and tetanus vaccines, refusing vaccination leads to a higher risk of harm than vaccinating does.

Diseases such as distemper in dogs and flu in horses are now relatively rare, and this is in no small part due to the success of vaccination. But that is no reason for complacency. In 2007 Australia experienced a devastating equine influenza outbreak, with large numbers of horses falling prey to the disease and suffering greatly. The Australian national equine industry was shut down for months and incurred millions of dollars worth of damages.

Nonetheless, some horses are not good candidates for vaccination, for example the chronically ill or the very young. In this instance, the concept of herd immunity is essential – if 90 percent of the population in a herd is vaccinated, the remaining 10 percent will clearly have some protection conferred on them as the disease is denied the opportunity to circulate.

Vaccines are not usually covered by insurance companies, but they are relatively inexpensive – especially given the cost of treatment for vaccine-preventable diseases – and some may be specifically required for travel and/or competition.

What if I know my horse does not respond well to being vaccinated?

Some horses develop transient reactions when they are vaccinated, such as a sore neck. In general such reactions resolve within 24hrs. If you know your horse suffers from this type of reaction, please tell us when you book your appointment so that we can minimise your horse’s discomfort, for example by changing the type of vaccine, our choice of injection site or by giving an anti-inflammatory injection at the same time as the vaccine.

In the small number of cases where significant adverse reactions occur, robust procedures are in place to allow front line vets to inform manufacturers and their regulatory bodies, ensuring the risk of repeated events are minimised.

How soon can I ride after a vaccination?

You should try to reduce stress such as heavy exercise for 24-48 hours after vaccination. This will further reduce the very small chance of an adverse reaction. In most cases very light work such as a short hack can continue uninterrupted.

Equine Influenza (flu)

Equine flu causes fever, depression, lethargy, coughing and a watery or snotty nasal discharge. Disease spreads quickly between unprotected horses as the virus can travel great distances in the air. People travelling from infected to naive horses can also transmit infection by carrying virus particles on their hands, clothes or equipment. Although it is possible for vaccinated horses to become ill, the course of the disease is usually significantly shorter and the symptoms much less severe.

Flu vaccination rules for racing and competition

Each governing body sets its own flu vaccination rules, and they do not all match. The main ones are summarised below, but rules change, so please always check your own governing body’s current rules before you compete.

A flu vaccination course is made up of a primary course of two injections, a first booster (the third injection), then regular boosters after that. The main rules are:

• British Horseracing Authority (racing): for courses started since 2022, the second injection is given 21-60 days after the first, and the first booster 120-180 days after the second. After that, boosters must be no more than 6 calendar months apart. The horse’s latest vaccination must be within 6 calendar months of race day, but not within 7 days of it.
• FEI (international competition, and FEI classes held in the UK): for courses started since 1 January 2024, the second injection is given 21-60 days after the first, and the first booster within 6 months and 21 days of the second. Boosters are needed at least every 12 months, but to compete a horse must have had a booster within 6 months and 21 days of arriving at the event, and not within the 7 days before arrival. FEI horses must also have their flu vaccinations recorded in the FEI HorseApp.
• British Dressage, British Showjumping and British Eventing (national competition): boosters must be given no more than 12 months apart. British Eventing dropped its 6-month rule for national competitions from 1 January 2026. Primary course timings differ slightly between these bodies, so please check with them or ask us.

Under all of these rules, a horse must have had at least the first two injections before it can compete, and it cannot compete within 7 days of any flu vaccination.

If you compete under more than one set of rules, we can plan a timetable that meets all of them. As a guide, giving the second injection 21-60 days after the first and the first booster 150-180 days after the second fits all of the rules above. During flu outbreaks, governing bodies sometimes recommend extra boosters, so it is worth keeping an eye on their news.

Every flu vaccination must be recorded in your horse’s passport and signed and stamped by the vet who gave it. Please make sure the passport is with your horse when we visit to vaccinate.

It is important your horse’s boosters are given on time. If a booster is late, even by a day, the whole course will usually need to be restarted before your horse can compete again, and there is no leeway. The office will be happy to work out dates for you, but please note we do not send vaccination reminders, so keeping track of when boosters are due remains the owner’s responsibility.

Tetanus

Flu and tetanus vaccinations are usually given together as one combined injection. If your horse needs vaccinating against tetanus alone, a primary course of two injections is given about 4 weeks apart, followed by regular boosters. How often boosters are needed depends on the vaccine used, and is usually every two to three years once the course is complete. We will follow the manufacturer’s schedule and can tell you when your horse’s next tetanus booster is due.

Vaccinated pregnant mares should be given a tetanus booster in the last 4-6 weeks of pregnancy. This boosts the protective antibodies in the mare’s colostrum (first milk), which gives the foal protection for its first few months of life.

Horses are particularly vulnerable to tetanus but it is readily preventable through vaccination – every horse should be protected in this way. Tetanus is caused by a soil-dwelling bacterium, Clostridium tetani, found readily in the environment. The bacteria invade the body through cuts and grazes, and horses often acquire it through puncture wounds such as penetrations of the sole of the foot.

The bacteria multiply in the body and produce a toxin that causes a progressive rigid paralysis of the horse’s muscles. The horse becomes stiffer, adopting a rigid stance with an elevated tail head, and may also appear anxious and become sensitised to sensory stimuli such as touch, sound and light. Ultimately the horse has trouble eating, standing and breathing and even if treatment is instituted most will succumb to respiratory failure.

Vaccination is arguably medicine’s greatest triumph. Take advantage of it by working with us to design a schedule that suits you and your horses.