Auckland schools and childcare centres have been told to send home all unvaccinated children and staff if they get a case of measles this term.
The move comes as schools reopen today after a two-week holiday in which 70 new measles cases were reported across Auckland - almost half as many again as the 157 cases in the first six months of this year to July 4.
Two-thirds of the new cases (45) were in south Auckland, and the biggest group affected so far this year is children under 4 (43 per cent).
Medical Officer of Health Dr Julia Peters said almost 50 Auckland early childhood services and schools have now reported measles cases - about half of them early childhood centres, and including some where staff caught the disease first.
"Auckland Regional Public Health Service (ARPHS) will be asking schools and early learning services to check staff immunity," she said.
"With a new term, ARPHS expects a rise in the number of cases involving schoolchildren, meaning non-immune children and teachers exposed to the virus will have to stay at home, as well as the person with measles.
"Measles is one of the most highly infectious viruses, and anyone who has been in a classroom with a case is at risk of developing the illness if they are not vaccinated or immune. Non-immune staff and students have to go into quarantine at home for one to two weeks.
"Being in quarantine means staying at home, away from school, work, public places, transport and events like birthday parties and sports games."
Nationally, Environmental Science and Research (ESR) data shows that 88 of the 141 new measles cases reported from June 1 to July 12 were in the Counties Manukau health district.
ARPHS figures show that a further 33 were reported there in the week to July 19, taking the total for South and East Auckland and Franklin to 125 so far this year.
Incoming Auckland Primary Principals Association president Heath McNeil, from Ormiston Primary School in east Auckland, said he would ask his staff today to check that their measles vaccinations were up to date.
"We haven't had that conversation with staff. We need to, as adults, keep up good records," he said.
An ARPHS spokeswoman said health services could check the immunisation status of all children born in NZ since 2005 on the National Immunisation Register.
McNeil said immigrant children were not on the register but most migrant source countries had similar immunisation policies as New Zealand.
The register does not cover older teenagers and adults born before 2005 so they may need to check with their family doctors to see when they were last vaccinated.
Children are supposed to get vaccinations for measles, mumps and rubella (MMR) at 15 months and again at 4 years old. Getting both jabs gives them a 99 per cent chance of lifetime immunity, and even one jab provides 95 per cent immunity.
ARPHS is currently advising doctors to give infants their first MMR jab at 12 months instead of 15 months because of the current measles outbreak.
Doctors have also been asked to call in all children aged between 1 and 5 who have not received at least one MMR jab.
Immunisation Advisory Centre director Dr Nikki Turner said anyone unsure if they have had measles vaccinations should ask their parents or just ask their family doctor for a new jab.
"If you don't know, just get vaccinated," she said. "It's free, and if you are already vaccinated there's no risk in getting vaccinated again."
Anyone aged 50 or over does not need to be vaccinated. They are considered to be immune already because measles was widespread in their childhood.
Ministry of Education deputy secretary Katrina Casey said schools could not legally stop a child attending school unless they either had a communicable disease or were directed to stop them by a Medical Officer of Health.
ARPHS said it was relying on advice to parents rather than invoking its power to direct them.
Measles symptoms include a high fever, runny nose, cough and sore red eyes.
A few days later a rash starts on the face and neck, and then spreads to the rest of the body.
You can have measles and spread it to others before you feel sick or show any symptoms. - Source ARPHS