Measles has again become a global public health concern, highlighting the need to ensure anyone who will be travelling is adequately protected, experts say.

Measles is on the rise globally— with southeast Asia, including Bali, Vietnam and Thailand— experiencing periodic outbreaks and resurgences occurring in several places where the disease had been eliminated. The UK is one of six European countries that recently followed Canada in losing their measles-free status.

Australian cases increased threefold from 2024 to 2025, and over 73 notifications have already been made this year.

“The number of people that one person with measles can infect is about 12 to 18,” says microbiologist and infectious diseases physician Dr Bernard Hudson, Senior Staff Specialist in the Department of Microbiology and Infectious Diseases, Royal North Shore Hospital. “That’s actually the highest of all known infectious diseases.”

Herd immunity is key to prevention, with the measles vaccination target set at 95%, he says. “And it only has to drop down to 92% or less and you start to see outbreaks.”

Not all Australians are fully protected, however, with national data showing coverage rates for 24-month-olds were lower in 2024 than 2023 for both the first and second doses of measles-containing vaccine.

Dr Deb Mills, Medical Director of the Travel Medicine Alliance, adds that some adults have not had a second dose.

“People have one and they’ll think that’s enough,” she says. “Many people think they’re protected when they’re not.”

Assessing immunity status

The greatest risk comes from imported cases associated with international travel, and one infected person can rapidly spread the virus—even before they know they have it.

“In a susceptible population, up to 90% of people will get infected if they encounter someone with measles,” Dr Hudson says.

Before widespread vaccination programs started, most people had a measles infection in childhood. As a result, people born before 1966 have usually acquired natural immunity, Dr Hudson notes. Patients born later may not be immune unless they have been vaccinated or previously infected.

Before travelling, therefore, “anyone who’s born after 1966 should have documented evidence of two doses of measles vaccine or history of having had measles,” he says.

Children especially at risk

Infants are particularly vulnerable because maternal antibodies decline at around six months of age, Dr Mills explains.

But “in Australia, up until recently, we had no measles. So, it didn’t matter that we vaccinated at 12 months,” she says.

With the global outbreaks, the Australian Technical Advisory Group on Immunisation now recommends infants aged 6 to 11 months who will be travelling overseas receive an extra dose of a measles-containing vaccine.

This dose does not replace the routine schedule, although you do not need to repeat the early dose if it was given after 11 but before 12 months of age.

Importantly, though, parents may not know about it, Dr Mills says.

“People who are basically immune from their childhood going back to visit friends and relatives will take their dear little babies back to these countries. They’re not having their measles vaccine between six and 12 months of age because they just don’t think of it. And unless the GP specifically asks, ‘will you be traveling with this baby?’, it could go under the radar.”

She suggests GPs ask parents about their travel plans for the next year at the six-week postnatal check.

Practice tip: If the infant needs vaccines for both measles and TB, they must be given either together or one month apart.

Parents who are planning to travel to countries with high tuberculosis incidence (defined as ≥ 40/10,000) should be aware that the BCG vaccine is recommended for some children aged under 5, based on an individual risk assessment – but it needs to be given on the same day as MMR, or 4 weeks apart, since both are live parenteral vaccines.

Waiting lists for the BCG vaccination can be long, “so it requires some planning,” Dr Mills says. “I’ve got people booking in their babies even before they are born.”

Special considerations for immunosuppressed patients

Dr Hudson notes MMR vaccines contain live attenuated viruses, and decisions about vaccination in immunosuppressed individuals can be complex.

“If you’ve got someone who’s on immunosuppression, you should be asking for specialist advice about what to give and what not to give,” he says.

According to the Australian Immunisation Handbook, MMR-containing vaccines are contraindicated in people who have compromised immunity resulting from a primary or secondary medical condition or using some immunosuppressive agents (such as B-cell depleting biologics).

However, they may be considered in specific types of immunodeficiencies, when conditions that compromise immunity are well-controlled, or after immunosuppressive treatment has been completed, it states.

Breakthrough infections can still occur

About 93% of people are protected after receiving one vaccine dose, and about 97% after two, Dr Hudson says—which is high, but not perfect.

“Some of the measles cases have actually been in people who have had two doses of the vaccine.”

These infections tend to be milder and can present differently to usual, he says.

“The illness may not look like the typical rash measles. And because they’re not very sick, it may not be recognised.”

These patients may still contribute to transmission, he adds, although they are probably less infectious than someone who hasn’t been vaccinated.

Even local travel can put people at risk

While international travel is the main pathway by which measles enters Australia, local travel is not risk-free.

“Everyone should know their measles vaccination status irrespective of where they’re travelling,” Dr Hudson says.

Check state and territory health department websites for exposure alerts.

Key takeaways

• All patients planning travel should have their measles immunity status reviewed
• Check for documented evidence of two doses of measles-containing vaccine or prior infection in people born after 1966
• Infants aged 6 to 11 months who are travelling overseas should have a dose of a measles-containing vaccine, but they will still need to have the standard 2-dose schedule when due.
• Vaccinated patients may develop mild illness that does not resemble classic measles
• Seek specialist vaccination advice in patients who are immunocompromised.