Alongside excellent biosecurity, vaccination provides the best possible protection against Strangles. As an outbreak of Strangles has both welfare and economic consequences to a herd, control of the disease is an important aspect of stable management. We recommend that all horses in a stable yard be vaccinated to provide the best protection against the disease. The vaccine is not 100% effective but horses are much less likely to show signs of illness and signs are less severe. Crucially, the rate of abscesses developing is vastly reduced, which in turn means that horses are much less likely to become carriers of disease and the rate of shedding of the bacteria will be significantly reduced. Biosecurity is still very important and an isolation period of 2-3 weeks for new horses entering a yard is advisable, especially when coming from high-risk situations such as dealer yards or group transport.
Prevention is better than cure
The Strangles vaccine - Strangvac, became available in 2022. We now have the benefit of three years’ experience of its use in about 10,000 horses throughout Europe, along with a scientific review published in the Equine Veterinary Journal in 2024.
Why vaccinate against strangles?
The vaccine does not inject live bacteria into the horse, so strangles cannot occur as a result of vaccination. Approximately 5 per cent of horses experienced heat, pain or swelling at the vaccination site - in the muscle, similar to influenza and tetanus vaccines - which either resolved by itself or with anti-inflammatory medications, such as Bute. Only very rarely were other adverse reactions reported.
Is the vaccine safe?
The following side effects are seen quite commonly:
• An increase in body temperature lasting 1-5 days.
• A swelling (possibly hot and sore) at the vaccination site.
• Runny eyes lasting for 1-5 days
• Loss of appetite for up to 1 day
And, like all vaccines, more serious complications such as anaphylaxis are possible but are very rare
What are the potential side effects?
A primary course of two injections about a month apart are given. Horses must be healthy at the time of vaccination.
• 1st Vaccination from 5 months of age.
• 2nd Vaccination 4 weeks later.
• 3rd Vaccination 6 months following the first vaccination.
The original data sheet recommends a booster vaccination at 2 months in high-risk situations. However, antibodies are known to last for at least 12 months. A pragmatic approach has been adopted throughout the UK and Europe with boosters being given every 6-12 months, following the initial course, the frequency depending on risk assessment by vet and owner. Should the horse be exposed to a known case, immediate revaccination will maximise protection. Booster vaccinations which run over by more than one month should be restarted, as data demonstrating immune memory beyond the 12-month period is lacking.
The vaccine is not licensed to be given alongside other vaccines, but extensive anecdotal evidence has shown no increase in adverse events if given at the same time as flu or tetanus vaccines, making it a practical option.
What is the vaccine schedule?
In theory, if all horses were vaccinated, it might be possible to eventually eradicate strangles. However, this is unrealistic, and efforts should be concentrated to vaccinate horses at medium to high risk:
• Horses at livery yards with movement on and off the yard
• Horses travelling to training, competition or stud
• Horses which are thought to have contacted a clinical case.
• Premises frequently accepting new horses or with a high population of young horses.
• Premises where maintaining optimal biosecurity is difficult
• Horses attending ‘enthusiastic amateur’ competitions where biosecurity may be suboptimal.
• Equestrian businesses where closure would be untenable or livery yards with horses of mixed ownership.
Which horses should be vaccinated?
Yes. Vaccinated horses can be differentiated from horses which have developed antibodies as a result of disease: this means that the blood test that is commonly used to screen horses for recent exposure to Streptococcus equi equi can be used in vaccinated horses. The vaccine also does not interfere with guttural pouch scope results.
Can the vaccine be used in conjunction with the Blood test for strangles?
No, the vaccine does not contain live Strep. equi or Strep. equi DNA. Therefore, horses that have been vaccinated will not test positive for strangles in diagnostic culture or PCR tests, unless they have been recently infected with Strep. equi.
In addition, the vaccine does not contain the proteins used in the strangles blood tests, so vaccinated horses will not test seropositive unless they have been exposed to Strep. equi.
Can a vaccinated horse become a carrier of the vaccinal strain?
Can the vaccine be used in the face of an outbreak?
Only healthy horses should be vaccinated. Even vaccinated horses can become infected and then infect others. The vaccine will reduce the severity of the disease and so is useful in the face of an outbreak, but the vaccine alone will not stop the disease spreading. If your horse has never been vaccinated against Strangles it takes two weeks after the primary course to confer sufficient immunity so may not be of benefit in the face of an outbreak.
My horse is the only one on the yard to be vaccinated, is there any benefit in this?
Yes, efficacy has been demonstrated for the individual horse to reduce clinical signs of disease in the acute stage of the infection.
Can the vaccine be used in pregnant mares?
The safe use of Strangvac in pregnant mares has not been fully established. Anecdotally, the vaccine appears to be safe for pregnant mares, but this is based on unpublished data so the risks should be discussed with your vet.
What is the minimum age for vaccination?
Horses can be vaccinated from 5 months old.
What is the cost?
The cost of the vaccination, as of November 2025, is £55, plus any applicable visit fees.
If you have any questions about vaccinating against Strangles, or want to discuss any of the above points further, please do not hesitate to contact us.
