Australia has approved its first-ever vaccine to protect koalas from chlamydia, a move scientists hope will halt the spread of the deadly disease that has caused sharp declines in populations of the beloved marsupial, already at risk of extinction.

The single-dose vaccine is now ready for nationwide use in wildlife hospitals, clinics, and directly in the field.

Chlamydia — a sexually transmitted infection that also affects humans — is responsible for up to half of all wild koala deaths. It can also lead to infertility and blindness.

“Some isolated colonies are being pushed closer to extinction every single day,” said Peter Timms, professor of microbiology at the University of the Sunshine Coast.

He noted that in parts of southeast Queensland and New South Wales, infection rates often hover around 50% and, in some cases, reach as high as 70%.

Developed after more than a decade of research by Timms’ team, the vaccine can reduce the likelihood of koalas developing chlamydia symptoms during their reproductive years and cut mortality among wild populations by at least 65%.

“It offers three levels of protection — reducing infection, preventing progression to clinical disease, and, in some cases, reversing existing symptoms,” he said.

The Australian government has pledged AUD 76 million (USD 50 million) toward saving koalas.

In 2022, the species was officially listed as endangered in Queensland, New South Wales, and the Australian Capital Territory. The country’s national koala monitoring program estimates between 95,000 and 238,000 koalas remain in those regions, with another 129,000 to 286,000 living in Victoria and South Australia.

Koala numbers have halved over the past two decades due to infectious diseases, habitat loss, climate change, and bushfires, according to the World Wide Fund for Nature.