Waipukurau School principal Tim Hocquard said yesterday that 6 per cent of the student population had been asked to stay away, either because of not being immunised or awaiting confirmation that they were immune to the infection.
There were also a few teachers absent as well until they had proof of their immunity status, he said.
He would not give exact numbers but said about 1 per cent of the students at the school, which the Education Review Office said had a roll of 266 in May last year, had not been immunised.
The Ministry of Health was offering blood tests for those who did not have their immunisation records to determine if they were immune, he said.
Dr Eyre said it was not known where the child who had mumps had got them from but that it was a widely-circulating epidemic across the country this year - the last epidemic was in 1994.
She noted that in 2015 only 13 cases were recorded in New Zealand, 20 cases were notified in 2016, but to date 443 had been recorded this year - 57 of those in the last week.
"If we are getting 57 in a week the opportunities for anybody to get infected are out there, which is why we are trying to build awareness."
To date, Hawke's Bay had got off lightly because of its high immunisation coverage. she said.
The mumps/MMR immunisation was introduced to New Zealand in 1990 for children aged 12 to 15 months. A second dose was introduced in 1992 for children aged 11.
The two-day schedule that's operating now, where children were immunised at 15 months and 4 years old, was introduced in 2001.
People that were born before 1981 were considered immune as mumps was more widely in circulation at that time, Dr Eyre said.
Many people over that time may have contracted the infection and not even realised, but the fact it could have more serious implications, such as loss of hearing, swelling of the brain and spinal cord (known as meningitis) and swelling of the testicles, which could result in sterility, meant immunisation was introduced.
People could be infectious for two days before they noticed symptoms, including painful swelling of the saliva glands below the ear, high temperatures/fever, headaches, muscle aches and tiredness.
Mr Hocquard said the non-immune children that were away from Waipukurau School could continue their lessons through online programmes, and teaching materials were available for parents to pick up.
Dr Eyre said the main message to come through from this situation was that children needed to be fully immunised.
"It's the best protection."
