Moves are underway to target young people aged between 10 and 29 who may have missed out on the MMR vaccine as the Government tries to stamp out the worst mumps outbreak in 23 years.
All Blacks Rieko Ioane and Jack Goodhue contracted the highly infectious disease in Auckland and are among the 740 cases of mumps the Auckland Regional Public Health has been told of since January 1.
The large majority of cases have been reported at Auckland's three DHBs, followed by much smaller numbers at Waikato DHB and Southern DHB.
The majority of cases are children aged between 10 and 29 with experts warning the reported numbers are likely to be "only a fraction" of actual cases.
The Ministry of Health is in discussions with the Auckland Regional Public Health Service and DHBs about running a measles, mumps and rubella vaccine catch-up campaign to reach 10-29 year-olds who appear to the biggest age group who are not immunised against mumps.
University of Auckland senior lecturer in vaccinology Helen Petousis-Harris said there was a large cohort in New Zealand of children in the at-risk age group who had a low mumps vaccination uptake.
"The only way we are going to prevent these kind of outbreaks is to focus on that cohort that are likely to have low coverage."
The majority of children aged under 11 had received one dose of the MMR vaccine, but between 10 and 29 there was a low uptake. People aged over 30 would have had mumps and were therefore immune.
She said vaccinating the target age group in school had been floated among health experts to help counter the disease, but this might be logistically difficult if school nurses were required to do it.
"In the 1990s for example our coverage in some parts of our population for example were around 50 per cent even lower. So we've got this legacy of that."
New Zealand has a current immunisation rate of 93 per cent for all vaccines at age 2. The national register does not hold records for children over the age of 10.
"Think about whether you or your children have had the MMR vaccine. What struck me is it is very easy to think you have or that your children have had two doses and actually be wrong and of course we forget."
People who had no documented doses of the MMR vaccine were eligible for two free recorded doses.
Auckland Regional Public Health Service medical officer Dr Josephine Herman said Auckland's worst outbreak since 1994 had initially been sparked by cases from the Pacific Islands - mostly Fiji, and later Tonga - where the mumps vaccine was not available.
Along with targeting the at-risk age group, Auckland Regional Public Health Services was also working with Pacific providers across the city's three DHBs to educate them about getting the MMR vaccine.
There had also been "massive" outbreaks in the US and the UK, she said.
"In terms of where the mumps infection is occurring, it's actually all throughout the world. New Zealand has been immune to it until late last year and early this year. Because we've had a vulnerable population here who have not been fully immunised with the MMR vaccine, it's allowed community spread to be well established."
The Ministry of Health had an advisory on the Safe Travel website advising travellers to make sure they had the MMR vaccine before travelling to some Pacific countries because of the high risk of contracting mumps.
What is it:
Mumps causes swelling in the glands around the face
Can lead to meningitis in about 1 in 10 people
Mumps is spread through the air by breathing, coughing and sneezing, or through contact with infected saliva (ie, kissing, sharing food and drink)
Pain in the jaw
Swelling of the glands around the face
If you've caught mumps, it usually takes 12-25 days before you get sick. You'll be infectious from 1 week before swelling appears until 5 days after
Best protection against mumps is the measles, mumps and rubella (MMR) vaccine
Two doses of MMR vaccine protects about 85 percent of people from mumps
Most at risk:
People aged 12 to 29 years are at greatest risk of catching mumps, as they're the group least likely to have been fully immunised as children
People born in Fiji, Tonga, Kiribati, Nauru, Papua New Guinea, Solomon Islands, Tuvalu, Vanuatu and some Asian countries who may not have been offered mumps immunisation
Source: Ministry of Health