Health authorities are concerned about a sharp drop in vaccination rates in Northland

Ministry of Health data show rates have decreased since early 2017.

Total rates in Northland have fallen 5.7 percent to 64.2 per cent vaccinated as at March 2019.

Northland Maori immunisation rates have dropped to 53.4 per cent.

The figures follow a nationwide trend, where just 77 per cent of six-month-olds are having their vaccines on time.

Coverage of at least 90 per cent is needed for herd immunity.

Anything below this puts children at risk of vaccine-preventable diseases, particularly whooping cough and measles.