Students from a Hamilton middle school are in quarantine after parents sent an unimmunised child to school with the measles.

All students from Berkley Middle School who have not had two doses of MMR (measles) vaccine, must stay at home in quarantine for ten days and are not able to return to school until May 22.

Two siblings, one at Berkley and one at Hillcrest High School, were the first confirmed cases of measles in the Waikato for 2015.

Medical officer of health Dr Anita Bell said by following this advice, it should mean that all further cases will not be at school while they are infectious and there will be no need to extend the quarantine period.

"The [high school] student was not thought to be at school during her infectious period, so letters were sent to the school to raise awareness," she said.

"The sibling is at Berkley and we've had confirmation today of a rash so we will quarantine those who are unimmunised."

Berkley parents were also being encouraged to provide their child's vaccination records to confirm they have had two MMR doses and if they were unsure, to leave their children at home until they could provide confirmation.

Bell said documentation for middle school and high school-aged children was difficult to record.

"Sometimes documentation for the MMR for this age group is difficult to find," she said.

"Once you have had two MMRs then you are fully immunised or if you have had the disease you get full immunisation."

Bell said the high school student most likely caught measles during an overseas holiday and the younger sibling then contracted it.

"We believe that [the measles] was probably imported from a holiday abroad at Easter," she said.

There were 124 confirmed cases of measles in the Waikato last year and the outbreak was linked with a strain that plagued Auckland.

Of those cases, only four had been immunised.

The outbreak began at Fraser HIgh School and spread to four other schools in the Waikato.

"We learnt from early on last year with Fraser so we have the same practices in place but we need to be very clear that if you are not immunised you need to be in isolation, we want to reinforce that," Bell said.

"The ministry are aware that it is a national issue and not just a Waikato issue."

The incubation period for measles is two weeks and parents at Berkley have been asked to look out for symptoms in the next few weeks.

The first symptoms of measles are a fever, and one or more of a runny nose, cough and sore red eyes.

After a few days a red blotchy rash appears and lasts up to one week and usually starts on the face and spreads to the rest of the body.

Attempts to eradicate the virus in New Zealand began in 1969 when a universal vaccine was introduced but vulnerability remains high among unimmunised communities.

Immunisation advisory centre director of immunisation research and vaccinology Helen Petousis-Harris, said attempts to eradicate the virus began in New Zealand in 1969 but there were still groups that were unimmunised.

"We had a big epidemic in the early '90s and although our immunisation rates are quite good nationally (95 per cent are fully immunised), there are still those that are vulnerable," she said.

"The most common group of people that get measles are adolescents."

Bell said she encouraged parents to immunise their children and stressed the importance of vaccinations.

"The best protection against measles is immunisations," she said.

"Looking at last year, the most vulnerable population were 10-20 year-olds."

If your child was ill, parents were advised to phone their GP or Health Line on 0800 611 116 to seek advice as the measles virus was highly infectious.

Bell also encouraged parents to call population health on 07 838 2569, to confirm a possible diagnosis and prevent further spread.