A landmark study reveals that 1.7 million Australians lack sufficient immunity to measles, with immunity gaps among specific cohorts threatening the country’s measles elimination status amidst rising imported cases.
Australia may be carrying a larger measles vulnerability than many people realise, with a landmark study led by the National Centre for Immunisation Research and Surveillance estimating that 1.7 million people, or 6.7% of the population, lacked sufficient immunity in 2019. The findings suggest the country was only just inside the level of protection needed to help stop outbreaks, even before recent declines in childhood vaccination rates.
The study, published in the Australian and New Zealand Journal of Public Health, combined national immunisation register data with serosurveys, which measure antibodies in blood samples to gauge population immunity. Zoë Croker, the study’s lead author at NCIRS, said the analysis offered the most complete national estimate possible using Australia’s latest serological evidence and whole-of-population vaccine records. She said the results show protection is not evenly shared and that the safety margin is slim.
The greatest gaps were found among infants too young to complete the full vaccine schedule and among people born from the late 1970s onwards. Every birth cohort from 1977 onwards was estimated to have at least 5% susceptibility. The research also found that people aged 15 to 35 accounted for half of all measles cases recorded in Australia between 2008 and 2022, a group that often includes frequent overseas travellers and young parents.
The concern is sharpened by a sharp rise in imported measles cases. Recent figures from the National Notifiable Diseases Surveillance System show notifications climbing from single digits in 2022 to 181 in 2025, with 113 already recorded so far in 2026. The Australian Centre for Disease Control has also warned this year that measles is resurging globally and that adults aged 20 to 49 who are unvaccinated remain a particular concern. Its guidance says everyone born in or after 1966 should have two doses of measles-containing vaccine unless they have documented immunity.
Associate Professor Frank Beard, senior author of the study at NCIRS, said Australia has kept its measles elimination status since 2014, but that status depends on maintaining very high population protection. He warned that some communities and regions are likely to have much larger gaps than the national average, raising the risk of local outbreaks if the virus is introduced. The World Health Organization target for herd protection is generally understood to sit between 93% and 95%, and Australia’s estimated 93.3% immunity in 2019 was at the lower end of that range.
Public health officials are urging Australians, especially those planning overseas travel, to check their vaccination records and arrange catch-up doses if needed. The Australian Centre for Disease Control says two doses provide strong protection, and its guidance notes that vaccination, surveillance and rapid outbreak response remain central to preventing spread. For families with babies too young to be fully protected, the message is simple: closing immunity gaps in adults helps shield the most vulnerable children as well.
Disclaimer: This content is for informational purposes only and is not intended to be a substitute for professional medical judgment, advice, diagnosis, or treatment.
