State parliamentary inquiry backs Hendra vaccine use in horses

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A coloured transmission electron micrograph of the Hendra, virus. Photo: The Electron Microscopy Unit of the Australian Animal Health Laboratory, part of the CSIRO science agency CC BY 3.0 via Wikimedia Commons
A coloured transmission electron micrograph of the Hendra virus. Photo: The Electron Microscopy Unit of the Australian Animal Health Laboratory, part of the CSIRO science agency, CC BY 3.0 via Wikimedia Commons

A parliamentary inquiry into the Hendra virus vaccine in Australia has found no untoward safety issues around its use, although it has stopped short of making vaccination mandatory.

The Queensland Parliament’s Agriculture and Environment Committee made 11 recommendations arising from its eight-month inquiry into the vaccine and its use by veterinarians.

They include changes to workplace safety laws to limit the liability of veterinarians when treating horses that may have the virus.

The inquiry was sparked over concerns expressed by some horse owners of adverse reactions to the vaccine. The issue was further fueled by some veterinarians refusing to treat unvaccinated horses amid workplace health and safety concerns.

Hendra is a bat-borne virus which can be passed on to horses. In all, 77 horses are known to have died from Hendra infection since the virus was first identified in 1994. Seven people are known to have contracted the disease following contact with infected bodily fluids from horses. Four of those cases proved fatal.

The committee, in its findings, said it supported the rights of veterinarians to refuse to treat unvaccinated horses.

The committee’s recommendations include:

  • The revision of biosecurity guidelines for veterinarians to clarify requirements to wear personal protective equipment for low risk and high risk treatments of horses;
  • A feasibility study to examine whether exclusion testing for the virus can be performed in North Queensland as well as in Brisbane to give quicker test results for North Queensland samples;
  • Support from the government for the development of a rapid stall-side test for the virus;
  • Temperature indicators on the vaccine’s packaging to show whether it has been stored correctly;
  • Reminding vets of their obligation to provide horse owners with information about the vaccine and risks of adverse reactions;
  • More reporting of adverse vaccine reactions by horse owners to the regulatory body, the Australian Pesticide and Veterinary Medicines Authority; and
  • A campaign by the Department of Agriculture and Fisheries to promote vaccination against Hendra virus.

The committee also recommended the inclusion of equine industry representatives in future meetings of the Hendra Virus Interagency Technical Working Group that provides technical advice to the government.

The Queensland Government has three months to respond to the committee’s recommendations.

The Equivac HeV vaccine for horses was developed through a partnership between the CSIRO science agency’s Australian Animal Health Laboratory, Pfizer Health (now Zoetis), and international research partners in the United States.

The vaccine is manufactured and marketed by Zoetis. It remains the only equine vaccine developed in Australia.

The vaccine became available to veterinarians on November 1, 2012, under a Minor Use Permit. The vaccine received full registration from the Australian Pesticides and Veterinary Medicines Authority (APVMA) on August 4, 2015, having met the agency’s safety and efficacy requirements.

In relation to its assessment of safety in horses, the APVMA reviewed 21 separate efficacy and safety studies and 10 chemistry and manufacture studies, including peer-reviewed material in reaching its decision.

“Before granting registration of the product the APVMA was satisfied that the product — when used in accordance with the approved instructions — would be effective as an aid in the prevention of clinical symptoms of the disease caused by Hendra virus in horses four months of age or older,” the committee said.

The Department of Agriculture and Fisheries accepted the safety and efficacy of the vaccine as determined by the APVMA, it noted.

“Despite the assurances from the APVMA, the Department of Agriculture and Fisheries and others, horse owners have questioned the vaccine’s efficacy and safety.

“They argue that further testing of the vaccine is warranted on a wider range of horse breeds with differing genetic backgrounds.

“Horse owners have also claimed that veterinarians have not consistently provided them the manufacturer’s warnings and advice provided with the vaccine. It also appears that some veterinarians have deviated from the manufacturer’s guidelines and administered the vaccine together with other medicines and to sick horses.

“The administration of the vaccine contrary to the instructions is classified as ‘off label’. Where the off label use of the vaccine results in adverse reactions, those reactions are not classified as adverse reactions to the vaccine by Zoetis or the APVMA.”

The APVMA collects reports of adverse experience reports about the vaccine through its Adverse Experience Reporting Program.

The APVMA submission to the committee provided a breakdown for 1184 adverse event reports related to the vaccine it recorded to March 31, 2016. The APVMA categorises each report as either: “possible”, “possible/off-label”, “probable”, “probable/off-label”, “unknown” or “unlikely”.

According to the APVMA, 797 reports (67.3 per cent) were probable, 173 reports (14.6 per cent) were possible, 113 reports (9.5 per cent) were unknown and 93 reports (7.8 per cent) were categorised as unlikely.

The APVMA understood that 440,438 doses were administered during this period. This suggests an average rate of suspected adverse event reports (either probable or possible) of one reported adverse event for every 450 vaccination doses administered.

The APVMA classified only seven horse deaths as “possibly” related to the vaccine. No deaths were classified as “probably” related to the vaccine.

Zoetis reported slightly different figures based on 1255 reports it assessed as either “probably” or “possibly” related to the use of the vaccine. This translated to an approximate incidence for reaction reports of one in every 350 doses, or around 0.3 per cent of doses administered.

“Zoetis also advise that the vast majority of reported adverse reactions involve clinical signs listed within the vaccine label as potential side effects of the vaccine.”

The committee observed: “Submissions from many of the horse owners who participated in the inquiry and evidence given by at the committee’s hearings paint a different picture of adverse reactions to the vaccine.

“Rather than a statistical rarity, as the adverse reaction statistics provided by Zoetis and the APMVA would suggest, horse owners describe adverse events linked to the HeV vaccine as commonplace.

“The APVMA, Zoetis and the Australian Veterinary Association have argued that the levels of adverse reactions to the Hendra virus vaccine are low and well within the normal acceptable range.

“Despite these statistics, many horse owners are adamant that adverse reactions to the vaccine are more prevalent and under-reported (by vets to Zoetis to APVMA, and then reported by APVMA), and that vets and Zoetis have clear vested interests in not reporting adverse reactions.

“Horse owners also describe their disagreements with veterinarians over the diagnosis of their horses’ condition and, in some cases, the decision by veterinarians not to report their horse’s condition as an adverse reaction to the vaccine.

“To better understand how adverse reactions to the Hendra virus vaccine have been reported and handled, the committee conducted a short survey of horse owners, veterinarians and others to identify horse deaths they believed to be connected to an adverse reaction to the Hendra virus vaccine.

“Survey participants reported on 20 separate horse deaths since 2013, including sixteen deaths in 2015 and five in 2016.”

According to survey responses received:

  • Eight deaths occurred in New South Wales and twelve in Queensland;
  • Two of the deaths were not previously reported as adverse reactions to the vaccine;
  • In four of the twenty deaths reported, the horse died more than a year after the vaccination; and
  • Necroscopies were performed on four of the horses, and blood tests were conducted on seven.

“The survey results highlight some of the difficulties associated with the reporting and interpreting of adverse reactions to vaccinations,” the committee said.

Meanwhile, the Australian Veterinary Association (AVA) welcomed the committee’s recommendations.

A spokesman for equine veterinarians, Dr Nathan Anthony, said the inquiry had determined that the vaccine was safe and effective.

“Hendra kills and we congratulate the Agriculture and Environment Committee for acknowledging that Hendra represents a real risk and that the most effective option for preventing horse and human deaths from the virus is by horse vaccination.

“We have said all along that animal welfare, workplace health and safety and public safety are shared responsibilities where vets, government agencies and horse owners all have a role to play.

“So we’re particularly pleased that the report recommends that the Department of Agriculture and Fisheries mounts a campaign to promote the Hendra vaccine to horse owners and equestrian groups as a way of minimising the risk of Hendra infection.

“The committee’s recommendation for shorter turnaround times for exclusion testing will result in better horse welfare outcomes, and this was something we have been seeking for some time.”

Anthony said that the association was not surprised that the committee opted against calling for legislated mandatory Hendra vaccinations as there was no precedent for this in human and animal health in Queensland.

“The committee has however endorsed a recommendation of the AVA for the right of horse event organisers to insist on mandatory vaccination as a condition for entry into competition.

“In recent years, veterinarians in particular have had to consider increasingly complex risks in their decisions relating to Hendra virus.

“The committee has supported the right of vets to make their own decisions about treating unvaccinated horses.

“They have also made recommendations to change Workplace Health and Safety requirements so that vets are not responsible for creating a safe workplace for any person other than themselves and their staff when treating a horse suspected to be infected with Hendra virus.

“Overall, we are pleased with the recommendations and look forward to working with the government in implementing them.”

The committee’s report can be read here

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