Fears of waning immunity to measles vaccines have emerged after more than a dozen Victorians were hospitalised despite getting their injections.
Dr Katherine Gibney, infectious diseases physician at the Doherty Institute, says inadequate vaccination is to blame.
"Until 1992 we only gave children one dose of measles vaccine, then we worked out that two doses was better, so those people born before then likely only received one dose," she told 3AW.
Dr Gibney said people aged 54 and over were likely exposed to measles as a child, so are probably immune to the disease.
READ MORE: Measles alert for Bendigo and Heathcote area
"Certainly people who were born in the mid '60s or earlier, there was probably enough measles around that they got it as a child," she said.
"It's really that middle age, people born from the mid '60s through to 1990, who may not be adequately vaccinated."
Dr Gibney urged everyone born between 1965 and 1990 to visit their doctor.
"Our message is to make sure that everyone has two doses," she said.
"If adults are unsure if they've had a second dose they should really see their doctor."
Symptoms of measles include a fever, cough, runny nose and a distinctive rash.
However, the people who have recently been hospitalised with measles, despite having a childhood dose of the vaccine, have not had typical symptoms.
"They're really not presenting with the classic illness," Dr Gibney said.
"Their rash might not be exactly as you see in the textbooks, and they're less likely to have the fever and the cough."
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