Koalas—a lot of koalas— get chlamydia. And while humans can typically pop a few pills and get back to business in a few weeks, koalas don't respond well to chlamydia antibiotics. Current treatments disrupt the marsupials' gut bacteria, which are necessary to digest eucalyptus leaves.
Chlamydia infection in humans is caused by a similar but distinct bacterium, Chlamydia trachomatis. While antibiotics can easily treat chlamydia is people, they are not ideal for the marsupials.
The researchers hope the vaccine will help to improve the survival and reproduction of the animals, especially in parts of south-east Queensland and New South Wales where chlamydia affects more than half of koala populations.The Guardian
Common STIs like chlamydia, gonorrhea and syphilis increasingly resist antibiotics.