Chlamydial disease is a major threat to Australia’s endangered east coast koalas and can leave them blind, infertile and plagued by painful urinary tract infections.

Two years ago, researchers from the Queensland University of Technology began testing the vaccine on an isolated and shrinking wild population in the Gold Coast hinterland.

At the time the disease was rife, but the population now has a new lease on life after efforts to vaccinate 10 to 20 per cent of young wild koalas.

Modelling had suggested that level of coverage should have a significant impact and reduce overall instances of chlamydia and boost breeding capacity.

Two years into the five-year treat-and-track study, there’s every indication that’s happening.

QUT Professor Ken Beagley, who led the development of the vaccine, said 250 animals had been vaccinated so far, with 25 joeys delivered to healthy females.

There’s even a grandkid, with the daughter of a vaccinated female producing a healthy joey of her own.

“The results from this unique study are to date outstanding and have exceeded my expectations,” said Prof Beagley, who has put off retirement to see the project through.

“Importantly, all females and the joeys were chlamydia-negative at 12 months, with some still negative at 18 and 24 months.”

With three years of the study to go, the next steps involve securing extra funding and registering the vaccine.

“It is my passion. It is why I have not gone into full retirement,” Prof Beagley said.

“The number of joeys we have had and the fact that all of them are still negative for chlamydial disease is the most exciting outcome to date.”

It’s estimated chlamydia is present in about half of the nation’s koala population, with the infection rate as high as 90 per cent in some places.

It is a leading cause of death and compounds the effects of climate change and habitat loss – a terrible triple whammy that’s seen koalas listed as endangered in Queensland, NSW and the ACT.