More supplies of the ProteqFlu vaccine are due to arrive in Australia on Friday.
The vaccine has been strategically employed this week in setting up buffer zones in New South Wales and Queensland to strengthen containment efforts.
Queensland revised its original plan for a series of smaller buffer zones after fresh outbreaks in the south-east portion of the state's red zone.
"Although occurring within the red zone ... several inexplicable outbreaks have been occurred since 23 September 2007. These made the planned vaccination of buffer zones inappropriate," a spokesman said.
A large buffer zone around the known areas of horse flu infection is now being established in the South East Queensland Red Zone, a move that means eradication "may now occur over a longer period".
Both states have used vaccine to inoculate high performance horse populations, with a special shipment sent to Victoria to be used on horses destined to complete in the lucrative spring racing carnival.
Officials acknowledge that widespread vaccination alone has never resulted in successful eradication of the disease. However, it can be used strategically to create an area of horses with increased immunity to the disease to limit spread of infection out of south-east Queensland.
The buffer zone is 10km wide and stretches around the entire infected area in south-east Queensland.
In NSW, where containment efforts are said to be costing $1A million a week, authorities have confirmed that up to 600 local horses in the equine influenza (EI) buffer zone near Dubbo will receive horse flu vaccinations.
The state's chief veterinary officer, Bruce Christie, said: "Veterinary teams are being deployed to targeted horse properties today and it will take at least seven days to have the buffer vaccinations completed.
"Currently there are eight infected properties near Dubbo, including the first outbreak site near Brocklehurst," he said.
"I must make it clear from the outset that not every horse at Dubbo will be vaccinated. Only horses in the designated buffer area will be vaccinated to create a wall of immunity."
The disease is reported to have spread to horses stabled at the Dubbo racetrack, making racing at the venue unlikely until next year.
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