One in seven Australians unprotected from measles

About 1.7 million Australians were vulnerable to measles in 2019, according to a new study – and by now the figure is likely even higher, say researchers.
 
The landmark research, led by the National Centre for Immunisation Research and Surveillance (NCIRS), has revealed about 6.7% of Australians were not sufficiently immunised from measles in 2019.
 
Published in the Australian and New Zealand Journal of Public Health, the NCIRS study is a world-first, combining National Immunisation Register data with multiple serosurveys to reveal details of measles susceptibility across all age groups.
 
Researchers report overall herd immunity in Australia in 2019 was 93.3%. Although it sits within the World Health Organization target range of 93–95% for herd protection, ‘our margin is getting thinner’, says the study’s lead author and epidemiologist, Zoë Croker.
 
‘Because the global picture is deteriorating, we need ongoing effort to maintain that elimination status, which is required for that herd immunity threshold,’ she told newsGP.
 
‘While we have maintained our measles elimination status since 2014, protection isn’t shared evenly across the population, and the margin for error is relatively small. 
 
‘Importantly, population immunity may now be slightly lower than our 2019 estimate, given that childhood vaccination rates have declined since the COVID-19 pandemic.’
 
Several high-income countries, including Canada, Spain and the United Kingdom recently lost their measles elimination status due to rising global outbreaks and international travel.
 
In Australia, measles cases linked to overseas travel are rising, as are total numbers of reported cases since 2022. So far this year, 112 cases have been reported. 
 
Babies who are too young to have received their full measles vaccination schedule are among those most at risk of the disease, along with Australians born from the late 1970s onwards.
 
With many from this latter cohort now parents, they are also among Australia’s most frequent overseas travellers, increasing the risk of measles being brought back home.
 
Ms Croker is therefore urging GPs to check in with patients who are travelling overseas, to ensure they – and any children – are covered.
 
‘Infants under the age of 12 months aren’t routinely recommended to get measles vaccines, but if they are traveling to a country where measles is around, it is safe for those infants to get a measles vaccine after six months of age, and then still go back to their regular immunisation schedule of 12 months and 18 months,’ she said.
 
‘Particularly because of the increased risk for them, it is safe and effective for them to have a pre-dose, effectively a dose zero.’
 
Ms Croker reiterated that despite the focus on infants, which often led to the presumption of measles as a ‘childhood disease’, most cases still occur in adults.
 
‘Many of them only have one dose of vaccine on board, or they might have no doses at all just because of the changes in the vaccine schedule over the decades,’ she said.
 
Ms Croker said while she doesn’t believe Australia’s herd immunity is at ‘imminent risk’, she urged GPs to speak to their patients ‘to ask them to consider their measles vaccination status’.
 
‘People might be keen to get out of the cold weather and might head off to Vietnam or Indonesia or other countries where we know that there’s lots of measles going around, and ideally we don’t want them bringing it back,’ she said.
 
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