Could Chlamydia vaccination trials for Koalas have an impact on humans?

Chlamydia is caused by a bacterium that lives as a parasite inside human cells. If left untreated, it can cause long-term health problems. Chlamydia can permanently damage sexual organs and cause infertility in women and reduced fertility in men.

This Sexually Transmitted Infection (STI) is usually passed on through unprotected sexual activity with someone who has the infection. The bacteria can thrive in different parts of the body, including the penis, vagina, rectum and throat.

Interestingly Chlamydia has also spread extensively among Australian koalas, affecting half the animals in some areas. The koala is recognised globally as a symbol of Australia due to its distinctive appearance and a lot of research has been taking place into how the Koala population can be helped, including vaccine trials for this indigenous species.

The University of the Sunshine Coast stated that on 15 October 2021, the Australia Zoo Wildlife Hospital commenced a Phase 3 trial to vaccinate koalas against chlamydia. The trials, which began earlier in 2014, showed the chlamydia vaccine not only protects healthy koalas from developing symptoms but also reduces the severity of disease in already-infected animals. That is crucial because, while human chlamydia is somewhat easy to treat with antibiotics, the same strategy does not work in koalas.

Approximately 400 Australian koalas will have the chlamydia vaccine. Researchers say that the trial could play an important part in the longer-term survival of these marsupials. Amber Gillett, Veterinarian and Coordinator of Research at Australia Zoo Wildlife Hospital said, “It is a cruel disease that causes debilitating conjunctivitis, bladder infections and at times, infertility”.

Professor Timms, Professor of Microbiology at the University of the Sunshine Coast, said “as well as the initial rollout trial at Australia Zoo Wildlife Hospital, other trials were planned soon for Moggill Koala Rehabilitation Centre, RSPCA Wildlife Hospital and in several wild populations, including in the Moreton Bay region”.

One dose of the vaccine will be administered to the koalas, and they will then be microchipped and released. Estimates of koala populations differ as they are difficult to count in the wild. A 2016 study by the University of Queensland calculated there were around 330,000 koalas left in Australia.

Professor Timms commented in an article by the New Scientist that “it may be possible to use similar principles to develop a vaccine for human chlamydia, which is caused by the related bacterium Chlamydia trachomatis.” He added, “I think this trial will be closely watched by the human chlamydia vaccine world”.

Chlamydia is known as the ‘silent’ infection because approximately 75% of women and 50% of men do not have any signs or symptoms of any infection. Symptoms can include bleeding between periods, pain or burning during sex and urination, unusual discharge and genital discomfort and swelling.

The Australian Government Department for Health states that about 16% of Australians reports having an STI in their lifetime and that over 23,000 Australians are living with Human Immunodeficiency Virus (HIV). This means early testing, detection and treatment of all sexually transmitted infections is crucial.

If you have any questions about Chlamydia or your overall sexual health then please speak to one of our highly trained sexual health advisors, either via the phone or through our live online webchat.  Better2Know can also make you an appointment at one of their sexual health clinics near you and organise confidential consultations, appointments and STI testing.

[1] Smithsonian Magazine: Australia Begins Vaccinating Hundreds of Koalas Against Chlamydia in New Trial

[2] CNN/Reuters: Chlamydia is so widespread among koalas they’re getting vaccinated