Zoetis response to Hendra Vaccination Story

Zoetis Response to Recent Media Coverage


As you know, the Hendra vaccine is the best protection against Hendra virus. The APVMA recently registered Equivac HeV, after examining the real world results of 350,000 doses administered by Australian veterinarians.

Equivac HeV’s adverse event rate is less than 0.3% and the vast majority of reports are transient, typical vaccine responses.

Recent media coverage has reported that a small number of horses have died or suffered serious adverse events after Hendra vaccination. In each of these reported cases, important information and context was not included in the media report. The omitted information supports alternate theories about the cause of death for these unfortunate horses.

We set out below, information that Zoetis has about these unfortunate circumstances.


There was considerable regional media attention around this horse. A University of Queensland autopsy, however, showed that Bella had advanced cancer which had spread to her spinal cord. The pathologist gave the opinion in the post mortem report the clinical signs were explained by these pathology results.


The Zoetis Hendra Vaccination Registry records that Red was last vaccinated in July 2013. That is 9 months before any symptoms were reported in this horse.

None of the veterinarians that we understand to have been likely to have vaccinated this horse have any record of having done so within nine months of the occurrence of symptoms.


Maestro is reported to have displayed lethargy and malaise shortly after vaccination. These symptoms resolved within about a week.

The horse later presented as unwell over a week after the initial symptoms resolved, with a symptom of weight loss. Other signs, such as fever and oedema, were also reported. The horse was euthanased a number of weeks after the onset of these later symptoms. According to the ABC, the APVMA did not classify any of the later symptoms of the second illness (that occurred around 4 weeks after vaccination and which were connected with the decision to euthanase the horse), as related to the vaccine.


Bart had a reaction to the vaccine involving symptoms of anorexia, lethargy, pain, panting, pyrexia and difficult walking. These symptoms continued for 4-5 days after vaccination and then resolved.

Subsequent to the resolution of these signs, the horse developed chronic recurrent respiratory symptoms. An organism was cultured following endoscopy and a long course of antibiotics was prescribed. The treating veterinarian reported to Zoetis that the symptoms were greatly improved by the use of antibiotics.

What does a possible classification mean?

The APVMA has classified a small number of horse deaths as ‘possibly’ due to vaccination. This means the vaccine is one of a number of equally plausible causes of the horse’s death in the opinion of the APVMA. The classification does not indicate any likelihood that the vaccine caused the symptom. If the APVMA believed the vaccine was the likely cause of the death it would be classified as ‘probable’.

Is there a risk of over vaccinating horses?

Analysis of adverse event reports received after the administration of more than 380,000 doses, show that ongoing boosters do not appear to increase the rate at which adverse events are reported, nor the likelihood that reactions reported will be more severe.

We believe in the importance of Equivac HeV and the safety of the product. This is underscored by the fact that the APVMA registered the product earlier this month.

Hendra virus remains a deadly threat to horses and people. Two horses died from Hendra virus in June and July 2015, and in 2014 six horse owners were administered an experimental treatment due to the high levels of exposure they had to Hendra virus.

Hendra virus has killed more than 90 horses and 4 people. The incomplete reports of a small number of horse owners should not reduce your confidence in a vaccine that has now been administered more than 380,000 times to more than 115,000 horses.

If you have any questions regarding Equivac HeV please contact your local Zoetis Equine Representative.


Yours sincerely,

The Zoetis Equine Team