Health experts are urging Australians to check their vaccination status as the nation experiences its largest diphtheria outbreak in decades, with cases spreading from the Northern Territory into Western Australia, South Australia and Queensland.
Speaking with ABC National Radio on Tuesday, Federal Health Minister Mark Butler described the outbreak as “serious”, with 133 cases reported in the NT, 79 in WA, 6 in SA, and 5 in Queensland.
What is diphtheria?
According to the Australian Centre for Disease Control, diphtheria is “caused by toxin-producing Corynebacterium diphtheriae or, sometimes, Corynebacterium ulcerans bacteria”.
While it can “be carried in the body without causing symptoms”, it typically infects the throat, nose, airways and skin.
“Diphtheria causes severe illness and death. Even with treatment, up to 1 in 10 people with respiratory symptoms die,” says the Australian CDC.
“Diphtheria can spread easily in communities with low vaccination coverage.”
‘Outbreak highlights drop in vaccination rates’
Experts say the resurgence of the vaccine-preventable disease highlights declining vaccination coverage, booster gaps and longstanding inequities in healthcare access for remote Aboriginal communities.
Jaya Dantas, Professor of International Health in the School of Population Health at Curtin University, says the outbreak “is of significant concern” and “the worst seen in Australia in recent times”.
“For over 50 years, Australia had no cases of diphtheria, so this resurgence highlights a reduction in vaccination rates and boosters,” says Professor Dantas.
“We need all of the population in the Northern Territory, Central Australia, and WA in the impacted communities to be vaccinated or receive a booster with urgency.
“We need to expand vaccinations under the National Immunisation Program (NIP) where childhood vaccination is completely free under the scheme, but with the adults, it’s still not the case.”
‘High vaccination rates critical’
Dr Chris Blyth, a paediatrician and Co-Head of Infectious Diseases Epidemiology at The Kids Research Institute, says maintaining high vaccination rates remains critical to preventing outbreaks.
“Diphtheria is a rare but dangerous infection [that] can affect the skin, causing sores or ulcers, affect the throat, causing pain and making it hard to breathe, and in some cases, it can damage the heart and nerves,” says Dr Blyth, who is also the incoming President of the Australasian Society for Infectious Diseases (ASID).
“These vaccines have been used safely for many years and are very effective. They work by training the immune system to recognise and block the diphtheria toxin that causes illness.
“To keep diseases like diphtheria under control, we need very high vaccination rates across the community. If coverage falls, we start to see gaps where outbreaks can occur.
“Vaccination protects not just individuals, but the whole community. Keeping vaccination rates high at all ages is the best way to protect people from deadly diseases like diphtheria.”
‘Disease didn’t return by chance’
“Diphtheria does not return to a population by chance,” says Professor Adrian Esterman, Chair of Biostatistics at Adelaide University.
“Nationally, childhood vaccination coverage at 24 months fell below 90% in 2024 for the first time since 2016. That weakens community protection across Australia, not just in Aboriginal communities.
“Australian guidance recommends adult diphtheria boosters at 50 and 65 if more than 10 years since last dose, with a tighter 5-year interval for at-risk groups.
“Adult booster coverage, however, is not routinely monitored the way childhood coverage is. We do not know what we do not measure.”
Professor Esterman notes that while “in this outbreak, almost all cases are in Aboriginal Australians”, it “should not be framed solely as an Aboriginal health issue”.
“It is also a warning about gaps in vaccination coverage, overcrowded housing, and infectious disease surveillance that have been building nationally for years,” he says.
‘Misinformation costs lives’
Dr Matt Mason, a lecturer in Nursing and Academic Lead for Work Integrated Learning for the School of Health at the University of the Sunshine Coast, says this outbreak and its spread are “deeply alarming”.
“[It] represents a crisis that should not be happening in 2026. This is a vaccine-preventable disease. Every case represents a failure somewhere in our public health system,” he says.
“Over 98% of cases are affecting Indigenous Australians, with the vast majority occurring in remote and very remote communities, populations that already face significant barriers to healthcare access.
“We must be honest, this is not simply a matter of individual vaccine hesitancy. It reflects decades of under-investment in culturally appropriate, community-led health infrastructure.
“That said, vaccine hesitancy accelerated through the COVID-19 pandemic, combined with lagging booster uptake among adolescents and adults, has created dangerous gaps in herd immunity.
“Misinformation costs lives. We are seeing that in real time.”
‘A serious reminder of the importance of vaccines’
The Australian Medical Association (AMA) is encouraging Australians to review their vaccination status and catch up on vaccination and booster doses.
AMA President Dr Danielle McMullen says “the rise in diphtheria cases is a serious reminder of the importance of vaccines”.
“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 comeback,” says Dr McMullen.
“We are seeing that risk play out with diphtheria, and it is a timely reminder for Australians to check they are up to date with their vaccines and to talk to their usual GP if they have questions.”
