There are not enough children under the age of 5 in New Zealand protected against measles to stop a potential national outbreak, a new University of Otago, Christchurch study shows.

This is because the number of children receiving the first measles, mumps and rubella (MMR) vaccine is declining.

Revealed in the New Zealand Medical Journal, coverage for the first MMR vaccine has decreased from 95.1 per cent for children born in 2017 to 88.9 per cent for those born in 2020.

Children of Māori ethnicity (indigenous Polynesian people of mainland New Zealand) had the lowest coverage for the first vaccine and this declined over time, from 92.8 per cent for the 2017 birth cohort to 78.4 per cent for 2020.

Lead author Dr Nienke Hagedoorn, of the Department of Paediatrics, says immunisation coverage for measles is insufficient to prevent community transmission in children under 5. More than 95 per cent coverage for the first vaccine is required.

Nationwide catch-up immunisation programmes are urgently needed to improve immunisation coverage and prevent an outbreak.