A baby has been diagnosed with a new and serious strain of meningococcal W in Northland.

The seven-month-old is the first case in the region since an outbreak of the new strain last year.

The Medical Officer of Health, Dr Jose Ortega Benito, says the latest case shows how important it is for children to be immunised against it.

He says 14 thousand have been, but there are still nearly nine thousand Northland children who can take advantage of the free vaccine.

He says there are some areas in Northland where only 50 percent of the eligible children are immunised.