independent

Monday 22 April 2019

Anti-vaxxers can put animals' lives at risk

A risk benefit analysis comes out in favour of vaccination
A risk benefit analysis comes out in favour of vaccination

Pete Wedderburn - Animal Doctor

Anti-vaxxers are prominent in social media, sharing articles based on fear and fiction as if they were truth. When science based data is produced to counter these views, it's dismissed as propaganda for Big Pharma. And once somebody has been convinced to believe anti-vaccination stories, it's surprisingly difficult to dissuade them.

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".

In the human world, this is causing serious public health issues, with people refusing to have vaccines against common diseases like measles. A county in New York has declared a state of emergency over a measles outbreak that has recently infected more than 150 people.

The county is experiencing New York state's longest measles outbreak since the disease was declared officially eliminated from the United States in 2000. The best way to stop the disease's spread is a vaccination rate in the community of 92% to 95%., while only 73% have been vaccinated at the moment. A new emergency law over there makes it illegal for unvaccinated young people to go to public gatherings. Civil rights lawyers are currently contesting this.

This anti-vaccination trend is affecting the animal world too. 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. So even 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.

It is difficult to counter this type of situation, as people's views become so entrenched: the mere repeating of science based facts does not work.

One of the challenges is that while most of the fears and scepticism are unfounded, some reactions to vaccinations do happen, and exceptionally rarely, they can be very serious reactions. These serious reactions become the focus of antivaxxers, 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.

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.

So what vaccine reactions are seen in pets, and what is the incidence?

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 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 30000 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 the 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).

More seriously, it is true that there are two 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 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 a vaccination. This happens in less than one in ten thousand cases but it is devastating when it does develop.

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.

Sligo Champion

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