Health authorities in Australia are on high alert as measles cases rise sharply in 2025. This surge is driven by more summer travel and fewer children getting vaccinated. The National Centre for Immunisation Research and Surveillance (NCIRS) reports that early childhood vaccination rates have fallen below the crucial 95% needed for herd immunity, slipping to 89.7% nationally for two-year-olds. The number of children receiving their first MMR dose on time dropped by 11.4 percentage points since before the pandemic. Australia recorded 168 measles cases in 2025, nearly three times the 57 cases of 2024. Health departments in New South Wales and South Australia issued alerts after a "Boxing Day cluster" linked to a single infectious traveller spread measles. This person visited Westfield Marion, Event Cinemas, and Cockles Cafe in South Australia before flying from Adelaide to Sydney on Qantas flight QF748. Authorities are tracing passengers and visitors who may have been exposed. New South Wales confirmed three cases recently, all travellers from south-east Asia. Alerts cover multiple locations in northern Sydney, including hospitals and shopping centres. Western Australia also confirmed two cases linked to this cluster, including a child. Victoria reported a separate case from a traveller returning from Bali. The rise in cases began weeks ago with steady infections in Western Australia and Queensland. Queensland warned residents after a traveller from Bali arrived on the Gold Coast. Measles is an airborne disease and can linger in a room for up to 30 minutes after an infected person leaves. Health officials urge all Australians to check their vaccination status. Those born in or after 1966 who have not had two MMR doses can get a free booster. Typical symptoms include fever, cough, runny nose, and a red rash after several days.