A vaccine to protect Australia's koalas against chlamydia has been approved for the first time, a development that scientists believe could stop the spread of the deadly disease that has ravaged populations of the beloved endangered animal.

"Some individual colonies are edging closer to local extinction every day," Peter Timms, professor of microbiology at the University of the Sunshine Coast said in a statement on Wednesday. 

Chlamydia spreads through mating and birth in koalas, causing infertility, blindness, and severe infections that leave them too weak to climb for food.

In some populations in the states of Queensland and New South Wales, infection rates are often around 50% and sometimes as high as 70%, Timms said.

The vaccine could reduce the likelihood of koalas developing symptoms of chlamydia during breeding age and cut mortality among wild koalas 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.

Development of the vaccine has been supported by AU$749,000 ($495,000) from the government's AU$76 million ($49.9 million) fund to save koalas. Much of the rest of the fund has been allocated to large habitat restoration projects and the national monitoring programme.

Koalas were listed as endangered in 2022 in Queensland, New South Wales and the Australian Capital Territory. Australia's national koala monitoring programme estimates that between 95,000 and 238,000 koalas are left in those areas.

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