A total of 804 measles cases have been confirmed in Auckland, with an increase of 26 from Saturday.
In a media stand up this afternoon, Auckland Regional Public Health Service (ARPHS) medical officer of health Dr William Rainger said cases of the illness were increasing at a constant rate of around 18-19 a day.
The majority of those cases continue to be in Counties Manukau, but there are cases appearing in other parts of Auckland.
He said the age of people mostly affected were children under the age of 5 and those aged between 13 and 29 years old.
"We continue to have a relatively high rate of hospitalisations across Auckland, with some seriously unwell people, but no deaths," he said.
Rainger said last week there was a child who was "very unwell" - but he was unsure whether anyone had been diagnosed as critical.
"Measles is quite a severe illness so even if you don't end up in hospital or with serious consequences of it, you are away from school for a few days and it's a very unpleasant thing to have - so it's best avoided."
He said 1 in 1000 people would have serious of ongoing consequences, or fatality.
"The more numbers, the more likely it is that there will be a fatality.
"The other thing is, it spreads so very easily from person to person. One case of measles might infect another 15 - so there is a social responsibility dimension to this as well."
In regards to the suspected case of measles at the St Peter's College school ball, Rainger said they did not know the number of potentially at-risk people.
"But what I can say is it's a suspected case, it hasn't been confirmed as yet. We will get the blood test result back in the next couple of days and then we will work with the school accordingly," he said.
"Even if people were exposed to a confirmed case, they wouldn't be infectious until this coming weekend - so there is plenty of time to provide advice."
He said schools had reacted proactively in giving parents a heads up following the ball, but this reaction may have been "misinterpreted".
"We do know that people's concerns about the safety and effectiveness of MMR is part of what is behind that - but people can be very very assured that MMR is a safe vaccine and it is an affective vaccine," he said.
"People should have no qualms about having their children and themselves vaccinated."
Since the start of the year, Rainger said there had been 50 plus schools, and a similar number of early childhood centres, with confirmed cases.
"We have been working very closely with the Ministry of Education to support schools in terms of their response.
"It's a balance between protecting vulnerable people but also not inadvertently interfering with important events," he said.
Rainger said people should go about their daily lives and it wasn't proportionate to cancel events at this stage.
In order for the Minister of Health to shut down events, Rainger said one would have to think about the number of people affected, the severity, the stage of outbreak, and the impact on other parts of the country.
"I think with good immunisations outreach ... there is every chance in Auckland the rate of increase will slow and we will reach a plateau and then will be on the down slide. I can't predict when that will be - the answer lies with people who are not vaccinated getting vaccinated.
"I also have a degree of confidence that by taking these measures in Auckland and elsewhere in the country we can prevent this scale of event happening elsewhere in New Zealand."
In response to anti-vaxxers, Rainger said they were misinformed and misinforming other people.
"A relatively high proportion of people end up in hospital with this illness. We have had experts from Starship talking over the weekend about the frontline implications of particularly children having measles.
"It's not a trivial illness, it can be fatal, it can lead to people with serious and permanent brain injuries and it can be prevented by MMR, those are the scientific facts.
"It can't be said often enough, measles is a preventable disease, it is prevented by vaccination and vaccination is safe," he said.
Carmel Ellis, general manager for child youth maternity, said pop-up clinics in the region had "a busy weekend".
"Saturday and Sunday we saw over 300 vaccinations done at the pop-up clinics. We also heard from our primary care colleagues that they have been extremely busy providing vaccinations in their settings as well."
Ellis said a vaccination station would be set up at Manurewa High School tomorrow, with other school nurses providing the service from next week.
She said there are really good rates of immunisations for younger children, which they know because of the National Immunisation Register, but for those older than 14 years old there weren't sufficient registers.
"So we are finding it really difficult to find out how many people we need to immunise, or how many people aren't fully immunised - to have a target," she said.
However, she said the ministry had assured there was enough vaccine available at this time.
Hundreds of students could be exposed to measles this morning after an infected student attended a St Peter's College school ball on the weekend.
St Peter's has been notifying all schools that could be affected after the partner of one of its students was found to have measles.
Students from more than 20 other schools were also at the ball. It's not known how many were fully immunised or whether they came in contact with the student.
The student attended St Peter's ball on Saturday before their symptoms began to appear.
More than 20 Auckland secondary schools were then notified their students may have been exposed.
St Peter's College headmaster James Bentley said the affected student had attended as the partner of a college student.
He has asked all St Peter's parents to keep their sons at home during the contagious period from September 9-16 if they have not been vaccinated.
New Zealand's secondary schools rugby league competition last week scrapped its tournament, which was to be held at South Auckland's Pulman Park.
The measles outbreak has been worst in south Auckland and is disproportionately affecting Māori and Pacific Island people.
Organisers said they did not want to risk players from other parts of the country contracting measles.
However, the national School Sport NZ winter tournament is going ahead as planned despite the measles outbreak.
About 25,000 secondary school students are due to take part in the tournament, which is held at venues across the North and South Islands.
Chief executive Garry Carnachan said he was not aware of any teams pulling out as of this morning. Health authorities had advised this morning that the tournament could go ahead as planned.
On Saturday Dr William Rainger, the Auckland Regional Public Health Service medical officer of health, said it was up to event organisers to decide if their events should be cancelled.
"A medical officer of health does have powers to direct organisers of public events to cancel these, if there's a risk to public health ... the current level of risk of measles in Auckland doesn't warrant using these powers."
However, if organisers knew people attending were likely to have been exposed to measles they should seek advice from the service or other medical professionals about the risk.
"On the basis of this discussion, an event organiser might decide to cancel their event."
Schools have varying policies on whether their unvaccinated students can attend tournaments.
Rosehill College in South Auckland's Papakura is allowing unvaccinated students to attend sports events but if any cases are reported at the tournament those students are being sent home.
But at nearby Manurewa High School, where 14 measles cases have been confirmed, only immunised students are being allowed to attend the winter tournament week.
The school is thought to be the worst hit by the measles outbreak. In recent days 300 students were sent home from Manurewa High School as more cases were confirmed, and another 700 stayed home on Friday after the board asked kids to stay away if they could not confirm they were fully vaccinated.
Students who were unimmunised when they came in contact with someone with measles must stay home for a quarantine period but others are being allowed back today.
They have been asked to bring proof of their immunisation status to school this morning.
Unvaccinated students who are not thought to have come into contact with one of the 14 cases of measles are allowed back to school but have been warned they could be sent home again if they come into contact with a person with measles.
Principal Pete Jones said the school was creating its own database showing students' immunisation status.
On Tuesday a vaccination programme run by the Counties Manukau DHB would begin at Manurewa High, targeted first at those aged 15 or older.
The school is issuing consent forms for parents to sign before the vaccinations - but students aged 16 and over will not need parental consent to get their shots.
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