Study warns of measles risk with 1.7 million Australians vulnerable

Warnings of possible measles outbreak as study finds 1.7 million Australians are vulnerable In short: A new study has found an estimated 1.7 million people are susceptible to catching measles, according to 2019 data. The paper, to be published today, says susceptibility was high for key groups of Australians born from the late 1970s onwards. What's next? Travellers at a higher risk of bringing the disease into Australia are being urged to get another jab, as well as adults in at-risk age groups. An estimated 1.7 million Australians are not protected against measles, putting the country at risk of more outbreaks, according to new analysis from the peak immunisation research organisation. The National Centre for Immunisation Research and Surveillance (NCIRS) study found almost seven per cent of the population was susceptible to measles in 2019. The paper will be published today in the Australian and New Zealand Journal of Public Health, and lead author Zoë Croker said susceptibility was high for key age groups of Australians born from the late 1970s onwards. The number of people susceptible included Australian babies who were not yet eligible for measles immunisations. "The concern is that there will be more measles outbreaks that will be harder to contain," Ms Crocker said. "We'll start to see more cases and a higher chance of there being a death associated." 'A warning sign' Ms Crocker said the world-first study combined blood samples testing measles immunity, with vaccination data and represents the most comprehensive national estimate currently possible. The analysis found overall measles immunity was 93.3 per cent, which epidemiologist Adrian Esterman said Australians must take as a "warning sign". "[That] is not good enough. That means that we are at risk of getting major measles outbreaks,"Professor Esterman said. "We don't really want it to get any worse." The World Health Organization has a target of achieving 93-95 per cent vaccine coverage, to establish herd immunity and prevent the spread of measles. Australia achieved measles elimination status in 2014 but continues to have imported cases in overseas visitors and returning residents. There were very few measles cases in Australia during the pandemic, but numbers have increased in the past two years. Who is at risk and why should we be worried? Anyone who is not fully vaccinated is at risk. Babies and young children are particularly at risk because they are not routinely vaccinated until 12 months old. So are those with reduced immunity and unvaccinated pregnant women because they can not be immunised while pregnant. The paper identified the key age groups with higher levels of susceptibility to measles, which included infants and young children and people aged 42-49 years, 31-33 years and 25 and 26 years. Ms Crocker said those groups were highly susceptible because of generational gaps in immunisation programs. "The biggest gaps are in people born around the year 2000, as well as those born in 1993, 1994 and 1995, which was when that second dose of measles-containing vaccine was introduced," she said. "Close behind are people in the early vaccine era, so born in 1977 to 1983… they're more likely to only have a single dose of measles-containing vaccine." Ms Croker said people born during or since 1966 may also be more susceptible because they may have missed vaccination altogether or only be partially vaccinated. However, she said some of these people may have life-long immunity from childhood measles infections. Professor Esterman, from Adelaide University, said the numbers were daunting. "We are at that stage where we need to be worried, we do not want our coverage rates to drop any more than they are now,"he said. "If a single infectious person goes into a room with a group of people who haven't got immunity, they will infect, very quickly, 12 to 15 of them. It's the most infectious disease we know about." Overseas travellers urged to get another jab Travellers are a higher risk of bringing measles into Australia, according to NCIRS associate director Frank Beard. "We'd strongly encourage people in the current climate of increasing global outbreaks of measles to check … records of measles vaccination," Dr Beard said. "If they haven't had good evidence that they previously received two doses at any time, then we strongly encourage them to get vaccinated again." Professor Esterman said those aged between 20 and 40 years old were catching measles during overseas travel. "Almost all of those cases are coming from people who've gone to Asia, so it could be the Philippines, Vietnam, Thailand, where they have quite large measles outbreaks … they come back and bring it with them," he said. "There's a huge role here for GPs. If a patient is going overseas and talks to a GP about what they need in terms of protection, the GP should immediately ask them, what's your measles status like?" Dr Beard said he would "strongly encourage" all adults in the at-risk age groups to consider getting another measles vaccine. 'We'll see more outbreaks' Ms Crocker said measles would circulate more throughout Australia if herd immunity dipped below 93 per cent. "It means that our public health system is less likely to be able to chase down every case and we are at a greater risk of measles then becoming more prominent in Australia." Professor Esterman fears Australia will fall below the threshold for herd immunity, which will lead to "more and more outbreaks". "It does mean that there will be some pockets of the Australian population which have got much lower coverage than that and that's where you start seeing these small outbreaks occurring," he said. "It's in those pockets of the population, which have got lower coverage rates. "This is telling us that there's something wrong, which we need to do something about." The latest immunisation data shows childhood vaccination coverage declined for a fifth year in 2025. Ms Crocker said her paper may "underestimate" susceptibility to measles, given childhood immunisation rates have dropped in recent years.