Immunisation of koalas against Chlamydia pecorum results in significant protection against chlamydial disease and mortality.

In 2022, the Australian Government listed the koala as endangered in several states due to habitat destruction, traffic strikes, dog attacks, and Chlamydia pecorum disease. This study evaluates a 10-year assessment of a Major Outer Membrane Protein-based vaccine's effectiveness against chlamydial disease in wild koalas from Southeast Queensland. Over a decade, 680 koalas were tracked, with five vaccine trials involving 165 koalas. While prior studies only offered up to two years of data, this study's extended period allowed a thorough evaluation of vaccine efficacy. Results showed that vaccinated koalas had significantly lower disease incidence, with a 64% reduction in chlamydial mortality. This vaccine demonstrated positive impacts on both male and female koalas, highlighting its crucial role in conserving the Australian koala population and mitigating the threats they face.