Since January 1, 2025, New South Wales has recorded 60 measles infections. Of those, 26 were locally acquired. Eight of those 26 have no known source: no travel history, no documented contact with a confirmed case. That is community transmission. In a country that was declared measles-free in 2014, that number should bother you.
The explanation is not exotic. Australia's first-dose coverage sits at 94.7%. Respectable. The second-dose coverage, however, is 89.5%. The herd immunity threshold for measles is 95% population immunity. You do not need a virology degree to see the problem. A 5.5-percentage-point gap sounds small until you remember that measles has a basic reproduction number (R0) of around 12 to 18, meaning a single infected person can expose a dozen or more susceptible contacts in an unguarded population.
The Virus Does Not Care About Your Good Intentions
Post-pandemic vaccine hesitancy gets blamed for a lot, and in this case, the blame is partly warranted. The COVID years corroded institutional trust in ways that are still working through the system, and that corrosion has a body count. But hesitancy is not the whole story here. Some of this is administrative drift: parents who intended to schedule the 18-month dose and did not, GPs who did not follow up, a system that assumed 94.7% first-dose compliance was close enough.
It was not close enough. The virus found the gap.
Vaccine skeptics will point out that measles circulates globally and that no domestic policy can seal borders against it. That is technically true. Indonesia ranked third globally for measles outbreaks in February 2026, per CDC data, and 32 of NSW's 34 overseas-acquired cases came from Southeast Asia. Import pressure is real. The fair concession stops there. A population at 95% immunity absorbs imported cases without sustained local transmission. Australia is not at 95%, which is why imported cases are sparking community spread instead of burning out.
The Number That Should End the Debate
Measles kills 1 to 3 people per 1,000 infections in high-income countries, which sounds low until you are one of them, or until you are an infant under 6 months old who cannot yet receive the vaccine and whose immunity depends entirely on the people around them being vaccinated. The two-dose MMR vaccine is 99% effective. Not 70%, not 85%. Ninety-nine percent. The gap between 99% efficacy and 89.5% coverage is not a scientific failure. It is a delivery failure.
Adults born after 1966 who received only one dose, or are unsure of their vaccination history, need two doses. That is not a suggestion from a cautious columnist. That is the standard recommendation from every relevant health authority. With Easter 2026 travel approaching and Bali still among the most common overseas exposure sites in the NSW data, the timing is not abstract.
Niall Johnston and Phoebe Williams at UNSW and the University of Sydney have noted directly that holiday travel periods accelerate import risk. The research brief writes itself: more travel, more exposure, more cases landing in a population that is 5 points short of protected.
State health departments need to run active recall campaigns for second-dose defaulters, the way they do for cervical cancer screening. GPs need to treat an incomplete vaccination record as a clinical finding, not a footnote. And anyone boarding a flight to Southeast Asia this month should check their MMR status before they check their luggage.
Australia eliminated measles once. The vaccine still works. The only variable that changed is coverage, and coverage is fixable.
