More than a decade after the World Health Organization (WHO) declared Australia free of measles, the country is facing a spike in cases. Many experts blame the international anti-vaccination movement, which is most prominent in the US.

As of October 7, there have been 133 cases of measles in Australia this year. By way of comparison, there were 57 cases in 2024, 26 in 2023, 7 in 2022, and none in 2021. Numerous cases have been imported from overseas, some of which have affected children too young to be vaccinated.

The current number of cases “doesn’t sound big by itself, but in context, it is part of a worrying pattern,” Josh Davis, MBBS, PhD, professor of medicine and public health at the University of Newcastle and infectious disease physician at John Hunter Hospital, Newcastle, told Medscape Medical News.

“It is concerning because measles virus is the most contagious known human pathogen. In an unvaccinated population, an average person with measles will infect 13-18 others. It spreads like wildfire.”

For this reason, the WHO recommends that at least 95% of a country’s total population receive two doses of the measles vaccine in childhood to create herd immunity. But while Australia has historically had high vaccination coverage, vaccination rates have been declining since the COVID-19 pandemic began. Some experts are now worried that Australia is at risk of losing its herd immunity.

Declining Vaccination Rates

Immunization coverage overall has declined across the country by 2%-3% since the pandemic began, said Frank Beard, MBChB, associate professor of public health at the University of Sydney, Sydney, and associate director of surveillance, coverage, evaluation and social science at the National Centre for Immunisation Research and Surveillance.

The two-dose coverage of the measles vaccine was 94% at 2 years of age before the pandemic and decreased to 92.5% in 2023. Some Australian regions have rates as low as 70%-75%. Moreover, the timeliness of measles vaccination has declined. In 2024, 1 in 3 children received the first dose of the measles, mumps, and rubella (MMR) vaccine late, putting children at risk of catching measles at a younger age.

“Any decline in childhood coverage is a concern, even if overall population immunity remains above the herd immunity threshold, as it will increase the risk of outbreaks, particularly as immunity gaps are much greater in some parts of Australia such as the north coast of New South Wales and the Gold Coast in Queensland,” Beard told Medscape Medical News.

He and his colleagues conducted a national survey of parents of young children last year. “Parents reported a range of access barriers, including difficulty getting appointments, costs associated with vaccination appointments, and difficulty prioritizing vaccination, along with concerns around vaccine safety and effectiveness and trust in information,” said Beard.

“There is certainly a lot of misinformation online, exacerbated by events in the US, which are likely contributing to parental concerns and questions, though it is difficult to quantify the contribution,” he added.

Research from 2024 found a large increase between 2017 and 2023 in the proportions of parents in Australia who believed that children receive too many vaccines, that vaccines cause autism, and that vaccine ingredients cause harm.

Other experts place more blame on the anti-vaccination movement than on health system shortcomings. Earlier this year, President Donald Trump picked anti-vaccine activist Robert F. Kennedy, Jr, as the US Secretary of Health and Human Services. The department has since faced budget cuts and mass firings. The US childhood vaccine schedule is also facing changes.

Davis considers the anti-vaccination movement, both in the US and Australia, to be the single most important factor in the increase in measles cases.

The Advisory Committee on Immunization Practices in the US recently voted to no longer recommend that children younger than 4 years receive the first dose of the combined measles, mumps, rubella, and varicella (MMRV) vaccine. Instead, the committee recommended that children aged 1 year through 3 years receive two shots: one for MMR and a second for varicella. The MMRV shot will be recommended as an option for a child’s second dose, which is given at around 4-6 years of age.

Building Trust and Understanding

Social media, too, is affecting vaccine uptake, Ramya Raman, MBBS, vice president of The Royal Australian College of General Practitioners and general practitioner in Piara Waters, Western Australia, told Medscape Medical News.

Social media provide platforms for spreading myths about vaccines, which may reduce uptake. “This is a global phenomenon affecting Australia. We’ve witnessed a doubling of measles cases over the last 2 years in Australia….Falling vaccination rates have created a perfect storm for the spread of measles,” said Raman.

Some regions in Australia are of particular concern, said Raman, such as the Northern Rivers region, as well as parts of inner city Melbourne and Sydney, where vaccination coverage has fallen to what she described as alarming levels.

“The number one thing you can do to help keep yourself, your family, and your community as safe possible is to get vaccinated,” said Raman. “Unfortunately, not enough patients are heeding that message. With elimination achieved a decade ago, some families underestimate risk — yet imported cases via international travel are now seeding local exposures.”

The National Immunisation Strategy for Australia 2025-2030 stresses the importance of engaging with communities to build trust and understanding in the value of immunization and to combat misinformation. These initiatives are crucial if Australia is to avoid losing its herd immunity, said Davis.

“Government agencies need to get on the front foot to counter and anticipate anti-vaccination rhetoric, and they should be vocally supported by academics and clinicians,” he said. “Catch-up vaccination programs should continue for those with delayed or missed vaccinations, and immigrants and refugees should be offered free vaccinations if they are not already vaccinated.”

Davis, Beard, and Raman reported having no relevant financial relationships.