Measles and diphtheria are back. Check your vaccination status.

The nine measles cases in South Australia in 2026 — the state’s highest since 2016 — came from a single traveller who contracted the virus overseas and attended Brighton Secondary School. Four people were infected through that one chain: three students and an adult. That adult, in their 40s, spent more than 24 hours in the emergency department at Queen Elizabeth Hospital while exposure contacts were traced.

Measles was declared eliminated from Australia in 2014. Twelve years later, an adult in their 40s is hospitalised from it.

South Australia’s Chief Public Health Officer Professor Nicola Spurrier has named the pattern she is watching: “I have seen our vaccination rates year on year since the pandemic starting to drop.” She has also spoken about what the pre-vaccine era actually looked like in clinical practice — “I’d see little ones die from these infectious diseases” — as a grounding note for a cohort that has never seen measles circulate freely.

The diphtheria outbreak is larger still

The diphtheria picture is distinct but runs parallel. Australia’s current diphtheria outbreak has exceeded 600 cases — the largest since national records began in 1991 — affecting predominantly remote Indigenous communities across four states and territories. South Australia recorded 22 cases. SA Health delivered over 4,500 vaccines to affected communities as part of the response, with case numbers now reported to be plateauing. That outcome required active, coordinated vaccination effort. It was not coincidental.

Diphtheria is a bacterial infection of the nose, throat, airways, or skin. It is treated with antibiotics, but severity depends heavily on how quickly it is recognised and managed. In communities with limited access to healthcare, that window narrows.

Both-and: hesitancy is not the primary driver here

The interpretation worth interrogating is that declining vaccination rates are primarily a hesitancy story. Adelaide University epidemiologist Adrian Esterman, cited in the ABC coverage, frames the more common barrier differently: “It’s things like parents being very busy, trouble getting to see the GP … rather than people hesitating to get their children vaccinated.”

That distinction matters both clinically and in terms of what fixes actually work. A parent who has deprioritised a GP appointment and a parent who has decided against vaccination require different responses. Esterman also contextualises where Australia sits globally: Canada has lost its measles-free status, the UK has lost measles-free status, and the United States is on the threshold. The conditions that allow a cluster to become an outbreak — gaps in population immunity — are present and widening in multiple countries simultaneously.

The contested framing is whether the responsibility lies with parents, GPs, the Medicare rebate structure that makes appointments harder to access, or national immunisation program communications. All of those pressures are real and simultaneously true. The disease does not wait for that argument to resolve.

2 cents

The most useful question this week is concrete: do you know your own vaccination status?

Adults born before approximately 1966 are generally considered immune from natural measles infection — the virus was endemic before vaccination became available. Those born between 1966 and 1993 typically received one MMR dose under the schedule of the time; the two-dose schedule was introduced in 1994. One dose provides strong but not complete protection. If you are in that window and cannot confirm two doses, your Australian Immunisation Register record is accessible via myGov. A second MMR dose is safe, available through your GP, and free under the National Immunisation Program for those without evidence of two prior doses.

For children: if a catch-up appointment has slipped, this week is a reasonable one to rebook it. The access barriers Esterman describes are real — and so is the clinical reality that measles, when it circulates in an under-vaccinated population, does not remain a mild inconvenience. Before vaccination, it killed.

Verdict: yes — worth checking your records and acting if you are unsure.

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Sources cited

1. Diseases of the past like measles and diphtheria are making a comeback — ABC News
2. Australian Immunisation Register — Services Australia