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Vaccination side effects

Vaccinations are proven to have significant benefits for the health of both humans and horses alike. But vaccinations – just like any medicine – can have side effects. However, any side effects to vaccines are generally mild and short-lived.

Think about when you get a flu or tetanus shot – the site of the injection might be sore for a day or so but any discomfort soon disappears.

Given that the diseases prevented by vaccination can be extremely serious or even fatal, the benefits of protecting your horse greatly outweigh the minimal risks.

Remember: there are no live or modified-live vaccines available for horses in Australia. So there is no risk of your horse developing the disease they are being vaccinated against, nor acting as a ‘carrier’ and spreading infection to other animals as a result of being vaccinated.

It is scientifically proven that vaccinations do not weaken or overload your horse’s immune system. Your horse comes into contact with many more antigens in its daily life than are contained in a vaccine.

If you’re concerned about side effects from a vaccination, please contact your vet.

Possible side effects from vaccinations

Possible side effects from vaccinations can generally be grouped into local symptoms that occur at or near the site of injection, or more generalised side effects that may occur more widely in the horse’s body.  Symptoms generally resolve without any need for specific treatment.

Local symptoms

These can include:

  • a lump, swelling or soreness at the site of an injection that gradually resolves over several days
  • slight muscle stiffness for a day or so.

Generalised symptoms

These can include:

  • temporary elevated temperature
  • temporary lethargy or loss of appetite
  • allergic reactions – these are rare but can occur and may require vet treatment. The most extreme form of reaction is anaphylaxis, which only occurs extremely rarely after vaccination.

How are side effects reported and classified?

Vaccine safety is treated very seriously and every suspected vaccine reaction is thoroughly investigated by the Australian Pesticide and Veterinary Medicines Authority (APVMA). Anyone can report a suspected vaccine side effect to either the vaccine’s manufacturer or the APVMA.

Side effects are classified depending on how likely it is that vaccination has caused a particular side effect:

  • probable – there is a reasonable likelihood that the vaccine caused the side effect
  • possible – the vaccination is one of several equally possible explanations for the side effect
  • unlikely – the vaccination is unlikely to have been responsible for the side effect
  • unknown – there is not enough evidence to determine whether a vaccination has caused a side effect.