Wild koalas begin trial of biodegradable chlamydia vaccine booster implant

Recapturing free-ranging koalas for a second injection can add handling stress and requires staff, time and access to the same animal weeks later. A delayed-release booster could therefore address a logistical barrier that has limited the practicality of two-dose vaccination in the wild. The supplied report links prior vaccination activity around Elanora with fewer chlamydia admissions and subsequent joey births, while an independent southeast Queensland assessment cited in the report found reduced disease and mortality in vaccinated wild koalas. Those findings support further evaluation, not a conclusion that the implant itself has yet delivered comparable results.

Chlamydia is described in the supplied report as a major threat to koalas in southeast Queensland and New South Wales. The project’s earlier field work required an initial vaccination followed by a recapture four weeks later for a booster, creating a practical constraint on vaccination campaigns. At Elanora on the Gold Coast, where more than 70% of koalas presenting to Currumbin Wildlife Hospital were infected in 2020, the report says admissions for chlamydia from the general area have since fallen by 75%. It also reports 41 joeys and 13 grand-joeys in a population previously described as highly diseased. An independent report for the Queensland government drew on swabs from more than 1,100 koalas at southeast Queensland wildlife hospitals and recommended prioritizing several high-burden local government areas for vaccination.

The early results are limited. Only five wild koalas from Burleigh had received implants when the report was published, and Bamse and one other koala were chlamydia-free at their one-month checkup; this does not by itself establish long-term protection or population-level effectiveness. The implant had previously been tested in captive koalas, but the wild trial is still being monitored. Researchers also note that Chlamydia pecorum genotypes are changing, so continued surveillance will be needed to assess whether the vaccine remains well matched to circulating strains.

Researchers plan to monitor Bamse for at least six months, assessing whether the implant delivers the intended booster and how the animal fares in the wild. Results from the five-koala Burleigh trial will be more informative than the initial one-month checks. Separately, recommendations for vaccination priorities in southeast Queensland may shape where future deployment is considered.