Why won’t they vaccinate? Aussie horse owners explain resistance to Hendra jab

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

Concerns about vaccine safety, cost, and effectiveness appear to be key drivers behind the low uptake of Australia’s horse vaccine against the deadly Hendra virus, research suggests.

Hendra, first identified in 1994, is a virus carried by native fruit bats in Australia. It causes periodic serious disease and fatalities in horses. Seven humans are known to have caught the disease from sick horses, with four of the cases proving fatal.

Horse owners in Australia are encouraged to vaccinate their horses against the Hendra virus to reduce the risk of infection, and to prevent potential transmission to humans.

However, after the vaccine was released in 2012, uptake by horse owners was considered slow, with an estimated 11 to 17% of horses in Australia vaccinated.

University of Western Australia researcher Jennifer Manyweathers and her colleagues set out to examine barriers to vaccine uptake and potential scenarios that might persuade them to vaccinate in the future.

A total of 210 people answered a 38-question online survey, which was promoted on the Facebook pages of 26 veterinary hospitals in areas where Hendra virus cases had previously been confirmed − in far north New South Wales, and South East, Central, and Far North Queensland.

The survey, open for six weeks in the first part of 2015, used a qualifying question to screen respondents so that only those who had not vaccinated all or any of their horses could proceed.

The researchers, writing in the journal BMC Veterinary Research, said just under three-quarters of the sample − 150 people − responded to the question concerning their reason for not vaccinating, or withdrawing from the vaccination program.

Each gave, on average, two to three reasons for not adopting vaccination as a protective strategy.

Three main themes revolved around their attitude towards the vaccine; their attitude towards authorities, including veterinarians and the pharmaceutical company that produces the vaccine; and risk assessment.

The “attitude towards the vaccine” theme reflected people’s concerns, including the potential for side effects, the protocol at the time of data collection requiring six-monthly boosters, and the cost and perceived safety of the vaccine.

Factors that would influence uptake of Hendra virus vaccination. Data has been rounded. Graphic: J. Manyweathers et al DOI: 10.1186/s12917-017-1006-7
Factors that would influence uptake of Hendra virus vaccination. Data has been rounded. Graphic: J. Manyweathers et al, DOI: 10.1186/s12917-017-1006-7

The “risk assessment” theme included evidence of people’s own risk assessment of their horses and property and the risk of vaccinating a horse that was unwell.

The theme “attitude to authorities” reflected consideration given by horse owners to the nature of the relationship between them and those in authority, and the relationship between authorities.

The cost of the vaccine was the fourth most frequently given single response (39 comments), but was only mentioned by eight respondents as their sole reason for not vaccinating.

“The cost was mentioned in parallel with the protocol at the time requiring six-monthly boosters and veterinary administration.”

Turning to factors that might persuade owners to vaccinate, the researchers identified six influencing factors in which 37 to 49% of respondents would reconsider vaccinating their horses:

  • If the vaccine was free.
  • If one of their horses became infected with Hendra.
  • If the vaccine was cheaper.
  • If a horse on a neighboring or nearby property became infected.
  • If the vaccine became available as an annual booster
  • If they could give the vaccine to the horses themselves.

However, the data also indicated that horse owners generally would not reconsider vaccinating their horses if advised by their veterinarian.

Discussing their findings, the researchers said the single most frequent reason given for non-adoption of vaccination was concern about side effects.

“Many respondents felt that the risk of side effects from the vaccine outweighed the perceived risk of Hendra virus infection.

“Lack of trust and confidence in veterinarians and the pharmaceutical company also featured prominently in comments as drivers for the non-adoption of the vaccine for horses.

“Comments suggested that the perceived lack of testing of the vaccine, and feeling that their horses were being used as ‘guinea pigs’ also resulted in an unwillingness to vaccinate.”

Responses regarding side effects that were thought to be inappropriately acknowledged by the pharmaceutical company also figured significantly, the study team reported.

They concluded: “Increased vaccination uptake could be encouraged by reducing vaccination costs and lowering concerns about the vaccine’s safety and effectiveness.

“The latter approach is challenging; more time and data may be required to convince a sceptical or distrusting audience. The qualitative and quantitative evidence that veterinarians are not trusted within this discourse is of concern.

“The need to rebuild and protect good relationships between horse owners and veterinarians should be highlighted as a priority issue, as veterinarians have the most direct and frequent contact with owners, particularly during disease outbreaks. Once lost, trust in veterinarians will be hard to win back.”

They said the study highlighted the fundamental paradigm shift that was required for policy makers, veterinarians, and researchers to fully understand and participate in the Hendra virus discourse.

“Such a discourse requires scientific facts but also needs, perhaps more urgently, a reconsideration of how risk perception, trust and decision making are considered.”

“Why won’t they just vaccinate?” Horse owner risk perception and uptake of the Hendra virus vaccine
J. Manyweathers, H. Field, N. Longnecker, K. Agho, C. Smith and M. Taylor.
BMC Veterinary Research 2017 13:103 DOI: 10.1186/s12917-017-1006-7

The study, published under a Creative Commons License, can be read here

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