Northland health authorities have asked schools to consider sending children home for at least two weeks if they have not been vaccinated against measles.
The move could affect about one in every six Northland schoolchildren based on the region's immunisation rates which the Northland District Health Board (DHB) says are "in the low to mid 80 per cents".
DHB chief executive Dr Nick Chamberlain wrote to all Northland principals yesterday saying the region's first two cases of measles had been reported in the past few weeks and there was a 95 per cent chance that any child with measles would pass it to other children within one metre of them.
"Once measles has spread, it has a mortality rate of one in 1000. That is why school children that come into contact with a child with measles must stay home for 14 days after contact," he told the principals.
He asked schools to check whether their students had been immunised and ensure that all unimmunised children and staff receive a measles, mumps and rubella (MMR) vaccination.
"Please consider excluding unimmunised children during this period of high risk, i.e. at least the next two weeks," Chamberlain wrote.
"If we have more cases, it could be longer, and we will keep you informed.
"I understand if exclusion seems too harsh or has too many unintended consequences or you simply just don't want to go there. So, if this is not possible, unimmunised children that are unwell with fever, a cough or cold, must be kept away from school as it could be the early [pre-rash] stage of measles."
Tai Tokerau Principals Association president Pat Newman said about 250 of the 400 students at his low-decile Hora Hora School in Whangarei had not provided their immunisation records to the school.
"When we enrol, we ask for them repeatedly," he said.
"Generally someone says we've lost them, and I can understand that to be honest."
He has asked the DHB to check its immunisation records for all the children who have not provided records already, and will then ask parents whose children have not been immunised to take their children to their doctor to get the jabs.
However, he said some parents were reluctant to go to the doctor because of unpaid debts for other family members, so he would then ask the DHB to vaccinate children at school if they can't get to a doctor.
Newman said there were also some children at the school who could not be vaccinated because of health conditions.
"I'm reluctant to send them home, but at the end of the day I've got to look at what's best for the whole school," he said.
"They say one in 1000 who are not immunised will die from measles, that is the figure from the DHB, so you know, if I was a parent, I think there is more risk to someone that is not immunised than there is in immunisation."
But he said he was waiting for advice from the Ministry of Education about whether schools had the legal power to exclude children on health grounds unless the DHB's medical officers of health invoked their legal powers to send children home.
The DHB has not yet taken that step.
Environmental Science and Research (ESR) says 111 cases of measles were reported nationally between January 1 and May 3. Only eight of those affected were fully vaccinated.