Monday November 28, 2022
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Equine vaccination: where are we now?

IMPORTANT REMINDER of CVFHPC CAMP requirements: to attend camp 2021 your horse must have had a booster AFTER 30th January 2021

What is equine influenza?

Equine influenza is a highly contagious viral disease that is endemic in Europe and North America. This means that it is always present and circulating at low levels. In the UK there are an estimated 460,000 leisure / pleasure horses. It is thought that 60% of these are un-vaccinated .

Minimum equine influenza vaccination requirements (for Pony Club, but not to Senior Camp, see above) :

The horse/pony must have received:

  • a first vaccination (V1) followed by a secondary vaccination (V2) given not less than 21 days and not more than 92 days after V1 (this is often referred to as the primary course)
  • and a third vaccination (V3), sometimes referred to as the first booster, given not less than 150 days and not more than 215 days after V2
  • further booster vaccinations at intervals of not more than a year apart
  • no horse/pony may compete on the same day as a relevant injection is given or on any of the 6 days following such an injection.

British Show jumping currently expect these minimum requirements

Vaccination requirements in excess of minimum requirements:

In the most recent DEFRA AHT BEVA Equine Quarterly Disease Surveillance Report it was concluded:
That horse owners, especially those attending gatherings and events attended by other horses, undertake routine influenza vaccination and ideally adopt 6 monthly booster vaccination as this is currently considered ‘gold standard’ for controlling this infection. The table below outlines how various bodies have adopted this gold standard approach.

Note that the horse must have had V1, V2 and V3 as above (see below for circumstances where only V1 and V2 have been given)

Governing body / competition level

Time frame in which booster is required prior to the competition or presence at a venue

Pony club competitions at Area level and above including Grassroots Regional Championships and the finals of the Winter Series competitions

6 months

Cheltenham racecourse requirements for CVFHPC camp

6 months before the last day of camp

BHA (racing) for all racecourses EXCEPT Cheltenham for CVFHPC camp

9 months (8 months plus 1 month grace period)


6 months and 21 days prior to competition

British eventing (BE)

The 6 calendar months prior to the day of the particular competition. For BE the vaccine can be given in the week prior to the competition but not on the day of the competition or entry to the competition venue

British dressage (BD)

6 months

Riding club (BRC)

6 months and 21 days

Certain venue specific requirements

Eg. Rectory Farm advises 6 months

CVFHPC CAMP requirements : to attend camp 2020 your horse must have had a booster (or V2) AFTER Feb 2nd  2020 (within 6 months of the end of camp)

How many days is 6 calendar months?

As the days in a month can vary it is best to use the shortest possible number of days that a 6 month period can be unless you are working it out for a specific event and a specific date. This is 181 days.

What if only the primary course has been given? Can I compete?

(ie. the first 2 vaccinations given 21-92 days apart – see above)

For minimum requirements:

  • if the second vaccination (V2)was given more than 215 days ago you will need to re-start the course
  • if the second vaccination was given less than 150 days ago you are fine to compete, but remember to ensure that you have the 3rd vaccination 150-215 days after the 2nd.

For situations where more than minimum requirements are necessary (Table above. Broadly speaking horses must have been vaccinated within 6 months of competition)

  • as long as the horse has had the first two injections that make up the primary course (V1 and V2), and the second injection was given within six months of the competition, you may compete. Remember than most governing bodies require 6 clear days after a vaccination before competing (BE does not, but it is a good rule to try and follow)

What if there are historical discrepancies in the passport

For example the horse was given his annual vaccination a few days late several years ago?

Some governing bodies now allow for this but it remains a grey area.

BE state that if the primary course (V1,2 and 3) is correct and the horse has had its most recent booster within the last 6 months, then the vet and the BE steward will make a discretionary decision.

Check the rules

It is important to check with the appropriate governing body’s rulebook on their vaccination requirements. These have changed a lot over the last year and it is likely that there will be further changes. If your horse does not meet their requirements it is likely that you will not be allowed to compete.

Passports and vaccination records

Horses/ponies must have a valid passport and vaccination record which:
must accompany the horse/pony to all events
must be available for inspection by the event officials
must be produced on request at any other time during the event

The Record of Vaccination against equine influenza must be completed by the veterinary surgeon who gave the vaccination, signed and stamped line by line.

Symptoms, strains and vaccines of equine influenza

From 2010 to 2017 all UK outbreaks have been caused by a strain known as American Florida Clade 2. The difference with the current outbreak is that cases involve American Florida Clade 1. Not only is a different virus strain isolated, but the symptoms of what is essentially a seasonal cold have been more severe than those seen previously. The three most characteristics signs of equine influenza are a raised temperature, coughing and nasal discharge. As with any virus there are longer term impacts on performance, which broadly speaking are more significant following more severe symptoms.

In the UK there are 3 licenced vaccines, all of which have passed the rigorous thresholds of the licencing procedure and there is no concern regarding performance of any of them.

Can a vaccinated horse get the disease?

The majority of cases of equine influenza have been in unvaccinated horses. There have been a handful of cases of flu in vaccinated horses, although the cases seen in vaccinated horses have been much milder. Most of the vaccinated horses that had disease had been vaccinated greater than 6 months previously.

Why change the booster requirement to 6 monthly?

It has been well reported in various studies that levels of influenza antibody in the blood are a good marker of protection against the virus. These antibodies peak after vaccination and then fall with time, and they do so more rapidly after a 6 month period. This fact informed the FEI schedules for 6 monthly vaccination.

“There is strong scientific evidence from both previous outbreak investigations and mathematical modelling projects to support that the herd immunity arising from adopting six monthly instead of 12 monthly booster vaccination will be enhanced.”

Dr Richard Newton Director of Epidemiology and Disease Surveillance at the Animal Health Trust

What are the side effects of vaccination?

As vaccination involves injecting a substance foreign to the body to trigger an immune response, it is not surprising that in a small number of cases there are obvious signs of an adverse reaction. These are usually mild, take the form of a sore neck or slight temperature, and are usually managed with rest and anti-inflammatories for a few days. Occasionally more severe signs occur, with rare reports of abscesses at the injection site. For this reason vets prefer to vaccinate clean dry horses to minimise the risk. Some owners have reported reduction in performance levels for short periods following vaccination. It is therefore sensible to vaccinate horses during quieter periods and to allow several rest or quiet days following vaccination.

Vaccination for other diseases


This disease is aquired through wounds contaminated with clostridial toxins, and not from other horses with the disease. However, for welfare reasons tetanus vaccination should be up to date. For most manufacturers after the primary course boosters are required every other year.

Equine herpes virus (EHV)

Although there is currently understandably growing concern regarding the outbreak of the neurological form of equine herpes virus-1 (EHV-1) infection affecting horses in southern England, EHV-1 is and always has been an ever-present threat among horses attending and mixing at equine events. This is because this common virus has the ability to remain in a latent (hidden) form within horses and re-emerge (become active) without warning to cause clinical problems. This is a similar phenomenon to that seen with herpes simplex virus in humans which periodically re-emerge to cause ‘cold sores’ in some people.

There are 5 types of equine herpes virus, but EHV 1 and EHV 4 are the most clinically important and they are the only types which can be vaccinated against. EHV 1 and 4 can cause a flu-like respiratory infection in horses but may also cause abortion in pregnant mares and severe neurological disease.

Currently vaccination involves a primary course of 2 vaccinations, and 6 monthly boosters. The available vaccine is licenced to reduce the severity of clinical signs. Researchers at the animal health trust are working on a more effective live vaccine to help limit the impact of this disease in the future.

If you have any concerns or further questions regarding vaccination then please contact your vets who will be happy to discuss the nature of the disease, prevention and the implications for you and your horse.

As horse owners we must remain vigilant about the whereabouts of outbreaks and limit disease spread with appropriate biosecurity in the face of outbreaks. This involves lockdown of premises where the virus has been identified and tracking and testing of in contact horses.

Biosecurity and vigilance at events

Advice for owners taking their horses to events and mixing with others can be found at


Please also note that from 1st October 2020 it will be compulsory for all horses to be microchipped, so if you are having your horse vaccinated over the next few months remember to check and chip if necessary.