The vaccine offering hope against the disease killing half of Australia’s koalas
The Australian icon is under threat from disease — but now there is hope.


First things first: Koalas are not bears. They’re marsupials, meaning females have a pouch in which their young can grow old enough to face the outside world; their specialist diet of eucalyptus leaves would be poisonous to humans, and they are the only extant member of their family, Phascolarctidae.
Now we’ve cleared that up, let’s get on with the news: there is hope after researchers at the University of the Sunshine Coast appear to finally have found a way to save them from the deadly chlamydia disease that has crushed numbers in recent years.
“Some individual colonies are edging closer to local extinction every day, particularly in South East Queensland and New South Wales, where infection rates within populations are often around 50 percent and in some cases can reach as high as 70 percent,” Peter Timms, professor of microbiology at UniSC’s Centre for Bioinnovation, said in a statement.
A baby koala being weighed with a toy to reduce it's separation anxiety from her mom pic.twitter.com/qDG1qNstFR
— Nature is Amazing ☘️ (@AMAZlNGNATURE) August 14, 2025
“The vaccine reduced the likelihood... by at least 65 percent”
Researcher Sam Phillips, who led the study, said: “This study found that the vaccine reduced the likelihood of koalas developing symptoms of chlamydia during breeding age and decreased mortality from the disease in wild populations by at least 65 percent."
“It’s based on Chlamydia pecorum’s major outer membrane protein (MOMP), and offers three levels of protection — reducing infection, preventing progression to clinical disease and, in some cases, reversing existing symptoms,” he added.
As well as the disease, koalas are also incredibly vulnerable to forest fires, human-induced habitat loss, and, tragically, being hit by cars. Such a decimation of their numbers has led to them being classed as endangered by Australia’s World Wildlife Fund (WWF).
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Koalas are also highly antisocial and can sleep for up to 18 hours a day. Now you’re on their side.
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