Northland DHB is offering to check the vaccination status of every school-child in the region, to help schools prepare for a measles outbreak.
The region's had only three cases so far this year, but it's expecting more given the dozens of cases in Auckland.
Chief executive Nick Chamberlain said the DHB was able to confirm that 50 children at Horahora school have not been vaccinated by checking their names against the National Immunisation Register.
The school was worried it might have to exclude or quarantine half its pupils because their parents didn't know if they'd had their shots or not.
Dr Chamberlain said the DHB is now offering to check the databases of all Northland primary schools.
He said there is no privacy breach involved because the only information shared is about vaccination - and that's a health benefit.
The National Immunisation Register holds the records of all children born after 2005.