Health authorities have confirmed six more cases of measles in Northland and are concerned it could spread.
A Hokianga girl was the region's first case after family visited from Waikato, where there has been a major outbreak.
Northland Health said on Monday that several members of her immediate family who weren't vaccinated have contracted the disease.
A young cousin may have infected more children, including unprotected babies, by going to pre-school last week.
Medical Officer of Health Clair Mills said those children and their parents have now been asked not to have contact with other unimmunised people until the incubation period ends.
Dr Mills said measles can have serious complications, and many children and young people in Northland have no immunity because of low vaccination rates.