Pete Wedderburn
15th January 2020 - 3 min read

Anti-vaxxers are people who are sceptical about/against vaccinations. Studies show that anti-vaxxers prioritise concepts like “pure” and “natural”. They have a mental block when it comes to accepting ideas that they see as “impure” or “artificial”. They classify pro-vaccination articles as “Big Pharma spin”.

three vaccinations and gloves

Anti-vaccination in the Animal World

This anti-vaccination trend is affecting the animal world as well as the human world. People who are sceptical about vaccinations are choosing not to have their pets vaccinated, and the consequence is that there is a rising proportion of unvaccinated dogs and cats. This does not cause immediate problems as with many animal illnesses, “herd immunity” kicks in as long as 70% of pets in an area are vaccinated. This ensures that fatal diseases like Parvovirus are unable to spread rapidly.

The Concern

If up to 30% of people choose not to vaccinate their pets, there will still only be rare, individual cases of animals dying from these serious illnesses. Problems start when the proportion of vaccinated pets falls below 70% when individual cases of infections are able to pass the virus on to other unvaccinated animals in their vicinity. Rapidly spreading, uncontrollable epidemics follow. Here in Ireland, this has not yet happened, but in Australia, some towns have suffered epidemics of Parvovirus, with dozens of under-vaccinated dogs dying. 

dog about to get injection

The Challenges

One of the challenges is that while most of the fears and scepticism are unfounded, some reactions to vaccinations do happen, and exceptionally rare, they can be very serious reactions. These serious reactions become the focus of anti-vaxxers, who disregard the science which explains that if you do a risk-benefit analysis, the benefits are so high, and the risk is so low, that it makes more logical sense to vaccinate your pet. 

Pete’s View

Even as I write this, I know that anti-vaxxers will be thinking “he would say that, wouldn’t he? He’s a vet and he has a financial incentive to get pets vaccinated”. It’s significant that vets who work for charities speak just as strongly in favour of vaccination as private vets. They would surely choose to vaccinate fewer pets (saving the charity money) if it was scientifically justified.

Reactions to Vaccines

So what vaccine reactions are seen in pets?

  • The most common reaction, as in humans, is mild swelling and pain at the site of the injection, which passes after a day or so.
  • Some animals experience a small rise in their body temperature, reflecting the fact that their immune system is responding the vaccine, so they may go off their food for 24 hours, and they may be quieter than usual.
  • Very rarely, in around one in 30,000 cases, an animal can suffer anaphylactic shock after a vaccine, collapsing and showing very dramatic signs of illness.  

Meanwhile, there is no evidence at all that vaccines cause a wide range of problems that are claimed, such as allergic skin disease, a wide range of cancers, and even canine autism (there is no such condition as this: it has been invented by anti-vaxxers).

Immune-Mediated Haemolytic Anaemia

More seriously,  it is true that there are illnesses that may, rarely, genuinely follow vaccination. Immune-Mediated Haemolytic Anaemia (IMHA) develops when the immune system attacks a pet’s own blood cells. While vaccination is regarded as a possible trigger, there are many other triggers, and in one recent study, the average time from most recent vaccination to the initial onset of illness was almost a year, making it hard to believe that vaccinations played a strong causative role.


Meanwhile, in cats, Injection Site Sarcoma is a malignant, challenging cancer that can develop at the site of vaccination. This happens in less than one in ten thousand cases but it is devastating when it does develop.

cat looking up at camera

It cannot be denied that bad reactions to vaccines can happen in exceptional cases, but neither can the immense benefit of vaccinations be denied. 

It’s up to each owner to decide what to do but my advice is to listen to independent scientists. If they say that the benefits of vaccination vastly outnumber the potential risks, then that’s enough for me.