Australia Faces Rising Diphtheria Outbreak Amid Waning Vaccination Rates

Australia is currently managing a significant resurgence of diphtheria, a highly contagious and potentially deadly disease. As of May 19, 2026, health authorities have confirmed a total of 223 cases, marking one of the largest outbreaks the country has seen in decades.

The outbreak originated in the Northern Territory and has since spread across three state borders, affecting Western Australia, Queensland and South Australia. One death has been recorded in the Northern Territory, though the exact cause of death remains under investigation.

The Australian Medical Association has issued an urgent warning to the public, urging all citizens to verify that they and their families are up to date with diphtheria vaccinations and necessary boosters.

Medical experts believe the resurgence is linked to a decline in vaccination rates. Dr. Danielle McMullen, President of the Australian Medical Association, noted that while immunisation is a major achievement of modern medicine, the return of largely eliminated diseases occurs when vaccination rates fall.

Immunisation is one of the greatest achievements in modern medicine, but when vaccination rates fall, serious diseases, which we had largely eliminated, can make a come back. We are seeing that risk play out with diphtheria.

Dr. Danielle McMullen, Australian Medical Association President

Data indicates that the number of fully vaccinated children in Australia has been declining since early 2020. Specifically, the percentage of two-year-olds who are fully vaccinated dropped below the critical threshold of 90 per cent in 2024.

This downward trend is believed to be part of a broader global decline in childhood vaccination rates following the COVID-19 pandemic, which may be contributing to the current resurgence of the bacteria Corynebacterium diphtheriae.

Under the National Childhood Immunisation Program, children are typically immunised against diphtheria at two, four, and six months of age. Health officials also recommend routine boosters for adults and adolescents in specific circumstances to maintain immunity.

Public health alerts have been particularly focused on regional areas. On April 24, 2026, health alerts were triggered in the Kimberley region of Western Australia, signaling the return of the disease to that area after nearly five decades.

Diphtheria is characterized by its high contagiousness and its ability to cause severe respiratory distress. The current spread across multiple states has prompted the Australian government to prepare emergency support as the situation worsens.

Health authorities continue to emphasize that the disease is vaccine-preventable and that maintaining high community immunity is the primary method for halting the spread of the infection across the continent.