The latest measles outbreak points to a growing increase in under-immunisation and international travel, experts say.
Australia has recorded about 112 measles cases this year, putting 2026 on track to exceed last year’s record tally as NSW Health warns of an outbreak in Sydney’s inner city.
NSW Health has issued issued a measles outbreak alert on 22 June for Potts Point, Darlinghurst and Sydney CBD.
Professor Adrian Esterman, Professor of Biostatistics at Adelaide University, told The Medical Republic the numbers were still relatively small but concerning given the much lower annual case numbers seen in recent years.
“There are three things happening at the same time which are causing the increase in cases,” Professor Esterman said.
The first was Australians’ tendency to travel to Southeast Asian regions, including Indonesia, Thailand, Vietnam, and the Philippines, which were currently experiencing outbreaks.
Executive director of Health Protection NSW, Dr Vicky Sheppeard, said that between January and March 2026, 60 measles cases were reported, 34 of which were acquired overseas, with only two occurring outside Southeast Asia.
“If a patient appears with a fever, cough, conjunctivitis, a rash beginning from the face down, the first thing GPs could ask is if they’ve been overseas,” Dr Sheppeard said.
“Measles is uncommon enough in Australian general practice that it wouldn’t sit at the top of most GPs’ lists of potential diagnoses,” Professor Esterman said.
He explained that Koplik spots, white specks that appear briefly two to three days before the full-body red rash, were an easy diagnostic sign of measles that could be easily overlooked.
The second prong, he said, was childhood vaccination rates, where “coverage has slipped for five years in a row. It was 95% in 2020, and it’s now more like 92.5%”.
Measles is among the most contagious diseases worldwide, infecting nine out of 10 non-immune people who come into close contact with or share enclosed airspace with an infected individual.
“We need very high vaccination coverage to achieve herd immunity,” Professor Esterman told TMR.
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Australian Immunisation Register data from the 2024 and 2025 assessment quarters showed that among one-year-olds, the ACT was the only jurisdiction to achieve the nation’s goal of 95% full immunisation coverage, followed by Tasmania at 93.16%, the Northern Territory at 92.64%, and Victoria at 92.47%.
Two-year-olds’ immunisation rates also varied, with the lowest measles, mumps and rubella (MMR) vaccination rate of 89.78% in Western Australia, followed by the Northern Territory and Queensland.
Across the nation, coverage rates for two-year-olds were about 90% – well below the target required for herd immunity.
In five-year-olds, the Northern Territory had the lowest full immunisation coverage at 91.66%, followed by Queensland with 91.79%.
Coverage rates were also subpar nationally for one and five-year-olds, at 91.54% and 93.17%, respectively.
“What we’re seeing is a slippage from 95% to 92.5%, which is not enough to cause a massive outbreak in Australia, but it is enough to cause small pockets of measles outbreaks among under-vaccinated children and adults,” Professor Esterman said.
The National Centre for Immunisation Research and Surveillance Australia’s 2025 survey found that parents of unvaccinated children most often doubted vaccine safety, believed vaccination didn’t protect others, and lacked trust in practitioners’ information.
Accessibility was the least cited reason among parents of unvaccinated children, while 46.4% of parents of partially vaccinated children did not prioritise vaccination appointments.
“The MMR vaccine is incredibly safe; it’s been around for decades,” Professor Esterman said.
“Vaccine hesitancy is a factor, but it’s not the whole story.”
Professor Esterman said practical access barriers, such as disruptions caused by the covid pandemic, including restricted travel and school closures, impeded access to childhood immunisations.
Thirdly, adults aged 20 to 49 years were occasionally under-immunised, he said.
Many in this demographic received only a single childhood dose – insufficient for those vaccinated before the 1992 two-dose MMR schedule – and were often unaware of their vaccination status, Professor Esterman told TMR.
The greatest current focus should be on administering catch-up doses to patients who couldn’t provide their immunisation records, he said.
Since NSW’s initial reports, Port Macquarie Base Hospital has been added as a new infection location from Friday, 19 June to Monday, 22 June.
