Humans aren’t the only creatures that can catch chlamydia: Birds, frogs, and other animals have been known to contract it, too. For koalas, however, the STD is exceptionally common—and therefore threatening to the animals' already dwindling population numbers across Australia.

In addition to transmitting chlamydia through sexual contact, female koalas can inadvertently pass it on to their offspring through their pap, a type of very nutritious fecal matter that joeys consume once they’ve grown out of breastfeeding (but aren’t yet old enough for eucalyptus leaves). According to National Geographic, scientists have treated chlamydia with antibiotics in the past, but those antibiotics may have an adverse effect on koalas’ ability to break down harmful tannins in eucalyptus leaves.

Now, there’s a preventive measure on the horizon: a vaccine. As NBC News reports, researchers at Australia’s University of the Sunshine Coast (USC) have administered an experimental chlamydia vaccine to more than 200 koalas, both captive and wild, and seen promising results.

“The vaccine has now passed Phase 1 and Phase 2 testing that has established that it is completely safe and produces a good immune response and a good level of protection,” USC microbiology professor Peter Timms said in a news release.

The team recently kicked off the third phase, which involves inoculating another 400 koalas at the Australia Zoo Wildlife Hospital. All koalas will also be implanted with microchips, so researchers can track any that end up back in the hospital in the next year.

Chlamydia can cause pink eye, bladder infections, infertility, and even death in koalas. That’s bad news for any species, but especially one whose overall population has plummeted 30 percent since just 2018, according to the Australian Koala Foundation [PDF]. Major culprits include wildfires, drought, heat waves, and land clearing.

Though protecting koalas (which, by the way, aren’t actually bears) from chlamydia can’t solve those issues, it could help make them more resilient while humans work to fix their habitat.

[h/t NBC News]