Inside the Hendra vaccine debate

There have now been around 120,000 horses vaccinated, and while many owners are happy with the results, there have been growing unverified reports of horses having adverse reactions to the injections.
There have now been around 120,000 horses vaccinated, and while many owners are happy with the results, there have been growing unverified reports of horses having adverse reactions to the injections.

With growing concern over the safety of the Hendra vaccine, Fiona MacDonald talks to vets and horse owners to get the facts

In July 2009, Dr Alister Rodgers was called out to a stud farm near Rockhampton, Queensland to examine a couple of horses that had fallen ill. The 55-year-old did a full physical and took blood samples, but couldn’t determine what was wrong. A few days later, one of the fillies died, and the post-mortem confirmed that she was infected with the Hendra virus. Unfortunately, Rodgers had been exposed.

He was rushed to hospital for anti-viral medication but his health quickly deteriorated, and at the start of September, he passed away, becoming the fourth person in Queensland to die from the Hendra virus since it was discovered in 1994, in addition to almost 100 horses.

Rodger’s death, which came just months after the death of another young Queensland vet, was met with renewed demand for protection against the virus.

Hendra is transferred from bats to horses via bodily fluids, and then from horses to humans in the same way, and so vaccinating horses was determined the best way for us to stay safe.

In 2012, after more than a decade of research by the CSIRO, an Equivac HeV was released, and the equine industry breathed a sigh of relief.

Three years on, however, and the vaccine is still waiting to be registered by the Australian Pesticides and Veterinary Medicines Authority. Despite this fact, it’s already been widely pushed out by vets and event organisers across Australia. And there are now growing concerns over the safety of the vaccine, how necessary it is in areas that aren’t exposed to bats and also how often it’s being recommended.

Early in 2014, vets reported that the uptake of the vaccine had been “disappointingly slow”. Most likely because the immunisation costs around $110 per dose, and requires at least
three doses to ensure protection, plus ongoing boosters every six months are currently recommended.

Then, on July 1, the industry’s national governing body, Equestrian Australia (EA), put in place a by-law strongly recommending the Hendra vaccine to all members, and stating that all horses from Queensland and New South Wales would need to be vaccinated in order to enter competitions. The by-law was met with strong resistance from members, and in February this year was revoked.

“It’s a fear campaign,” says Dr Matthew Walker, a vet with Thirlmere Veterinary Clinic in NSW.

“The vaccine’s been released on a minor use permit, which means it’s supposed to be used to control outbreaks of the disease, but they’re now recommending vaccination of horses in Wagga Wagga, Perth and Canberra—places where there have never been outbreaks.”

To be clear, Dr Walker isn’t against the vaccine and believes it would play an important role in stopping an outbreak, “but the way it’s being used now is unnecessary”.

“They’re scaring pony club mums with the vaccine campaign and making them think their children’s lives are at risk. It’s irresponsible,” he adds, referring to the campaign by vaccine-manufacturer Zoetis. Some of the ads rolled out contain images of children, vets and equestrian competitors, and contain emotive slogans such as: ‘Don’t gamble with your horse’s life—or your own’.

There have now been around 120,000 horses vaccinated, and while many owners are happy with the results, there have been growing unverified reports of horses having adverse reactions to the injections, ranging from localised swelling, hair loss, rashes and fever, to colic, and horses dropping dead in the days following the vaccine.

A coloured transmission electron micrograph of the Hendra virus.
A coloured transmission electron micrograph of the Hendra virus.

Seven horse deaths are currently being invested by the Australian Pesticides and Veterinary Medicines Authority (APVMA) for a possible link to the vaccine.

While Zoetis claims that reactions are possible with any vaccine, they’ve seen a reaction rate of less than 0.3 per cent—that’s 960 reactions out of the 320,000 vaccines administered so far. And the majority of these reactions are localised swelling at the injection site.

Vicki Roycroft, a six-time Olympic equestrian rider, has seen many of these side effects first-hand, however, and believes that can be more severe than Zoetis describes.

“I knew a horse who, after the first injection, was so swollen that it couldn’t feed in the paddock for a week. I understand a bit of a sore neck and swelling, but if a horse can’t put their head down to feed, that’s not right,” she says.

She’s also seen more severe reactions develop after subsequent boosters. “A neighbour’s horse had a reaction the first time she gave him the vaccine, so she decided to inject it into his chest the next time. The next day he developed laminitis problems. I’ve also seen horses getting really sick and horses are dying after the vaccine. Of course, the two could be unrelated, but there are too many coincidences.”

Equestrian rider Sue Vickery has had both of her horses react to the vaccine. “The first two reactions were quite mild. The horses were off colour, not eating for 24 hours and very lethargic. The second reaction was far worse, with a temperature of 39 degrees for 24 hours, muscle soreness and swelling after a short walk. They didn’t eat normal feed for four days,” she says.

“My older horse is now 16 and has ongoing wind problems, green mucus continually comes out of one or other nostril at random, and he doesn’t have the energy to be trained for more than 10 to 15 minutes.”

All these reactions experienced by horses are reported by veterinarians to Zoetis, who then passes them onto the APVMA for investigation, which is standard practice for all animal pharmaceutical products in Australia.

The vaccine itself has been thoroughly researched—it’s made up of a protein called sG, which helps the Hendra virus infect cells. Because it doesn’t actually contain any of the live virus, there’s no risk of infection from the vaccine. And veterinarian Dr Stephanie Armstrong, a spokesperson for Zoetis, explains that its safety isn’t in question when used on a healthy horse over the age of four months.

“Equivac HeV went through the same safety and efficacy testing any vaccine goes through prior to being released,” says Dr Armstrong. “Efficacy was proved through challenge studies and serology studies, while safety studies were also completed. The vaccine performed very well in all studies.”

Dr Armstrong explains that all of the safety and trial information has been submitted to the APVMA, and that the vaccine has now been ‘gazetted’ by the APVMA, which is one of the final steps before registration is finalised. A spokesperson from the APVMA added that this is a normal processing time for the registration of a vaccine. However, there are also concerns from horse owners about how often they’re being told to vaccinate. In the current APVMA permit, PER14876, there is no clear evidence to show that, after the first six-month booster, it’s necessary to keep immunising every six months.

Zoetis explains that this is because the data on how long the antibodies last following subsequent boosters is still being analysed, but this frequency was shown to be safe in their trials.

But without the conclusive research showing how often booster shots are really needed, many are worried that they are over-vaccinating their horses unnecessarily.

“We love our horses and we want to protect them with vaccines, but not over-vaccinate at the expense of their immune systems,” says Madeline Horne, a horse owner and equestrian competitor for Queensland. “We have performance horses—they are athletes. We need them healthy not chronically unwell and unable to fight off infection,” she adds.

Veterinarian Dr Stephanie Armstrong, a spokesperson for Zoetis, explains that its safety isn’t in question when used on a healthy horse over the age of four months.
Veterinarian Dr Stephanie Armstrong, a spokesperson for Zoetis, explains that its safety isn’t in question when used on a healthy horse over the age of four months.

While Dr Armstrong can’t respond to individual reports of adverse reactions without further investigation, she says the way it’s currently being used has been supported by their studies, which have been submitted to the APVMA, and it will now be up to the APVMA to make the final decision on the frequency of boosters.

“The Hendra vaccine has been in the marketplace for over two years now with some horses having received five or six doses. We have not seen any trend that indicates the risk of adverse events increases over time,” she explains.

“Unfortunately, the internet can be a great source of misinformation. Some horse owners can be worried by what they read online, but the stories online do not reflect the real world data from hundreds of thousands of doses and they’re very different to what I hear from equine vets I talk to.”

Dr Armstrong also reminds horse owners that the Hendra virus mortality rate is more than 50 per cent in humans and 100 per cent in horses, as any sign of infection will result in an animal being put down. “As with other vaccines, the benefits of vaccination far outweigh the minimal risks,” she adds.

Dr David Searle, a vet from the Illawarra Equine Centre in NSW, agrees that we should be wary of listening too much to unverified claims. “The horse owners all wanted this vaccine when the outbreak was there. We are listening way too much to a minority.”

His practice has vaccinated around 1800 to 2000 horses, ranging from elderly to young foals, and haven’t seen reactions more severe than fever and swollen necks. “Just what’s to be expected,” he adds.

What’s more worrying, Dr Searle explains, are claims that vets are now refusing to treat horses that aren’t vaccinated.

Jo Moore, a member of the Say No To The Hendra Vaccine Facebook group, from Queensland, has heard reports some vets are refusing to touch a horse until it’s been cleared of Hendra infection.

“One horse had a broken neck propped up with a hay bale for three days waiting for a negative Hendra result before the vet would attend and put him to sleep,” she explains.

While Dr Searle understands vets’ concerns, he explains, he would never put a client in a position where they felt pressured to vaccinate. “It’s important to keep it scientific. All you can do is tell clients the risk of Hendra in your area, the risk factors, the side effects of the vaccine, what it costs, and let them decide what they want to do.”

Dr Walker agrees. “If I had a horse within a 10-kilometre radius of where there’s been an outbreak, then I’d definitely vaccinate. But if you’re not in a risk area, is it worth risking the horse’s health by vaccinating?” he asks.

He believes it’s important to also remind people of preventive measures, such as wearing personal protective equipment (PPE) when in contact with sick horses, and reminding owners to clear or fence off any trees that house bats.

“Until the vaccine is a registered product, it should be used as it states on its minor usage permit, which is purely around the disease itself to stop outbreaks,” he adds.

Registration is something that Zoetis expects to happen in 2015, and with that will come APVMA recommendations on the frequency of immunisations, as well as reassurances over its safety.

Until then, vets can expect to have question from concerned horse owners, and will need to have all the facts to answer them.

“We need to listen to our clients and talk to them about their risks, instead of just pressuring them to vaccinate,” says Dr Walker.

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  1. Whoops, a bit of a typo here:
    “Dr Armstrong also reminds horse owners that the Hendra vaccine’s mortality rate is more than 50 per cent in humans and 100 per cent in horses, as any sign of infection will result in an animal being put down.”
    If the vaccine were that deadly then why are we using it? I think it is meant to say the Hendra virus mortality rate.

    • Thank you Mr Yeomans. You are absolutely right that is a typo and we have corrected it on the website. We will run a clarification in the next printed version also.

  2. The premise of your article that there is “growing concern about the safety of the vaccine” is nothing but sensationalism.
    By quoting only some selected Veterinarians and horse owners as the Magazine’s authoritative sources of “factual information” is biassed and to be deplored. Some of their quoted assumptions, portrayed as “fact” by the author and your Magazine are wrong.
    If this missive was unbiassed and a true portrayal of the “facts”, then who speaks for the horses and their owners who have been protected from infection by vaccination since 2012?
    Certainly not your author or the Magazine !

    • Dr Reid,

      Thank you for your interest in our magazine.

      As a magazine dedicated to the veterinary community, we include issues and subject matter that is topical, which has some kind of impact on the profession.
      While you may feel the growing concern from horse owners is sensationalistic, we respectfully disagree.
      I refer to the top of page 19 where we state, ‘there have been unverified reports of horses having adverse reactions to the injections’. Including the anecdotal evidence from horse owners was necessary to the article to alert our readers to what those concerns are.
      In its entirety, the article reported on the Hendra virus impact— the deaths of vets in Queensland and the horse mortality rate; also statistics and research from the Australian Pesticides and Veterinary Medicines Authority and most importantly comprehensive direct quotes from the vaccine manufacturer, Zoetis, that included factual information about the prevalence, the risks and the outcomes.
      We welcome any further information you think would benefit the veterinary community in a future edition.

    • Dear Editor
      Thank you for your response.
      FYI:- I wrote with considerable expertise in the field of Hendra virus and issues surrounding its prevention and treatment. If interested, then please research my 20+ years of intimate involvement since 1994 and my representations on prevention and treatment of this terrible disease with all levels of Government, with leading overseas research organisations in the USA, the Veterinary Profession, with Animal Health AUustralia Response Hendra virus Policy Brief, the intergovernmental Hendra virus Task Force , and with the Australian Horse Industry.
      I therefore feel most comfortable with my commentary and response to your published article.

  3. It is disappointing that this article is not balanced in opinion as the author fails to obtain the views of Veterinarians form the Hendra endemic areas of Northern NSW and Queensland who deal with proven HeV risk on a regular basis. Dr Matthew Walker a Veterinarian and breeder of Arabian Endurance horses is entitled to his own opinion, however it should be pointed out that his suggestion of Hendra risk within a 10 km radius of a previous outbreak lacks any scientific credibility. His suggestion that children are not at risk of HeV infection is not supported by the advice of Government agencies such as Health, Biosecurity, WH &S and also the Australian Veterinary Association; and in my opinion these claims are dangerously irresponsible. Last year 6 people from just 4 outbreaks (all people were not involved with the veterinary profession) had a significantly high exposure risk to warrant treatment with the experimental monoclonal antibody proving that Hendra risk extends beyond veterinarians. Hendra vaccination of horses in Queensland and Northern New South Wales is in the best interest of horse welfare and results in a significant public health benefit, this debate should keep this in perspective.

  4. Mr Anthony,
    Thank you for your interest in our magazine and our article on the Hendra vaccine.
    I welcome the opportunity for open discussion and would like to respond to some of your points.
    Firstly I can clear up your concern about Dr Walker’s quote regarding the exclusion zone. It was his opinion about whether he would use the vaccine and reported as such, “If I had a horse within a 10-kilometre radius of where there had been an outbreak, then I would definitely vaccinate.” This is the verbatim quote from Dr Walker in the article.
    Your next point about Dr Walker and the Hendra virus harming children. The article revealed his reaction to the vaccine’s advertising material and reported as such: “They’re scaring pony club Mums with the vaccine campaign and making them think their children’s lives are at risk. It’s irresponsible,” referring to the campaign by vaccine manufacturer Zoetis.
    The vaccine manufacturer, Zoetis was fully aware of the article and the information they supplied to us was included verbatim. We balanced this with the interviews of horse owners in infected areas and equine veterinarians.
    We completely agree with you that this is a very serious issue, particularly for the veterinary profession, which is why we have included this article in our magazine.
    Should we run a follow-up to this article, we would be very interested in including your opinion.

  5. “The vaccine itself has been thoroughly researched—it’s made up of a protein called sG, which helps the Hendra virus infect cells.”
    Surely this is also a typo? Shouldn’t it read ‘helps PREVENT the virus infect cells’?
    Also, something I have never been clear on… if this vaccine is a protein which acts directly on the virus by inhibiting its ability to invade the host’s cells, then why is there mention of ‘antibodies’ for Hendra occurring in the vaccinated horses?
    I thought that was how ‘traditional’ vaccines worked, by exposing the body to a ‘control’ version of the virus or bacterium, thereby stimulating a strong immune response if/when there is exposure to the ‘real’ pathogen?
    Can anyone clarify?

    • Vaccine can be a viral protein which the horses body will develop an antibody for. If then the horse were to be infected by the actual virus it would recognise this protein and attack it, thus preventing disease. In this way, the horse has developed immunity to the virus without the risk of it actually being infected like in a live-attenuated vaccine like you are referring to.
      Hope you understood.

  6. Why is the racing industry never refered to in these articles? What is their policy on Hendra Vaccinations? Surely they are as susceptible to Hendra as the rest of us and make up a large part of Australia’s equine community and yet seem strangley silent on the issue and rarely represented in articles like this one.

  7. IF these Vets spent as much time researching & understanding as they do arguing, marketing & selling this vaccine that is known to kill and permanently maim horses, they may just allay their fears and be able to get back to performing the oath they took & acting in accordance with the various Animal Welfare Acts. I would rather euthanize my horses that inject them with this, quite frankly! Take it back to from whence it came & get it SAFE!!!

  8. And what evidence can be produced that shows that the adjuvant in the vaccine is not the cause of adverse reactions? If horse owners have to prove that the vaccine caused the reaction, Zoetis should equally prove that the vaccine is not causing reactions?


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