Researchers are hopeful of combating a major threat to Australia's dwindling koala population thanks to a chlamydia vaccine trial in Queensland.
The sexually transmitted disease has spread widely among koalas and can cause infertility, further threatening a species already hit hard by bushfires, land clearing and climate change.
But 12 months after launching the trial, Gold Coast's Currumbin Wildlife Hospital believes there is hope after announcing Cassidy - a koala participating in their research - is pregnant.
The hospital's senior vet Michael Pyne said it was encouraging that Cassidy was expecting in an area where chlamydia runs rampant among the koala population.
The hospital - located at Currumbin Wildlife Sanctuary - admitted almost 500 koalas from the wild last year with 60 per cent of them suffering from the disease.
"It's encouraging that Cassidy is pregnant and negative to chlamydia, not only for the research trial but for the entire koala species," said Dr Pyne.
"It's still very early stages and too early to say if the vaccine will be a long-term solution, however Cassidy is making us hopeful."
The hospital has worked with Queensland University of Technology's Professor Kenneth Beagley to administer the chlamydia vaccine to 154 koalas before releasing them back to the wild in the last 12 months.
The trial hopes to track 30 koalas in the Gold Coast's Elanora area over three years, recapturing them every six months to check their immunity and reproductive status.
Professor Beagley kept his fingers crossed the trial would boost the species which has lost an estimated 30 per cent of its population since 2018, according to the Australian Koala Foundation.
"It's fantastic news that the vaccine has protected Cassidy and that she is now pregnant with a joey despite living in a population with a very high prevalence of chlamydia," he said.
"I do have cautious optimism for the future of the species. Hopefully, we can repeat this and see the koala population increase over time."