More than 1500 extra children were immunised against measles in the three weeks after the vaccination age was reduced in Auckland.
A measles outbreak in Auckland forced Auckland Regional Public Health to reduce the age children get their first vaccine from 15 months to 12 months as of June 12.
As of midday Friday, at least 161 people in Auckland have caught the highly infectious disease this year. Nationally, 274 cases have been reported in 2019.
Information released to the Herald showed 1555 Auckland infants received their first dose of the measles, mumps and rubella (MMR) vaccine between June 11 and 28 as a result of the lowering of the recommended age.
On top of that, another 769 children aged between 12 and 15 months across Auckland's three district health boards were given the vaccine in that time period because they were already scheduled or eligible to receive their first dose.
Waitematā DHB paediatrician Dr Tim Jelleyman said it was important all parents and guardians of unimmunised children aged 12 months and over visit their GP to get a free MMR vaccination, especially given this year's outbreak.
"Vaccination is the best form of protection from measles, which is a highly-contagious virus that can result in serious illness and death," he said.
Judging by current figures, this year's outbreak was expected to be the largest since 2011 when there were 597 cases.
During the 2014 outbreak, there were 280 confirmed reports across the whole year.
As of June 28, data from the Institute of Environmental Science and Research (ESR) showed 109 people had become so sick after catching measles they had been hospitalised this year. Fifty babies under 15-months-old had caught the disease and 31 of them needed hospital treatment.
Auckland Regional Public Health Service clinical director Dr Julia Peters said last week there had been 13 Auckland schools affected by the current outbreak, with measles cases at two central Auckland schools, six in Counties Manukau and five schools in West Auckland.
ESR public health physician Dr Jill Sherwood last week issued a reminder that it was particularly important people be aware of the disease as travel increased with the start of the school holidays, which began on Friday.
Yesterday, Regional Public Health Wellington put all those who were on Jetstar flight JQ263 from Auckland to Wellington at 4pm on July 1 on alert because an infected person travelled on the flight before they realised they had the disease.
The public health service also asked those who were around the Jetstar check-in terminal and gate 24 at Auckland Airport's domestic terminal between 3pm and 5pm on July 1 or around the Jetstar arrivals and baggage area in Wellington Airport about 4pm to keep an eye out for symptoms of the measles.
The infected person was also at Midnight Espresso cafe on Cuba St in Wellington on July 2 from 4pm to 9pm.
Medical Officer of Health Dr Craig Thornley said anyone who may have been in those locations at the relevant times and were unsure if they were immunised against measles should call their GP and advise them of the situation.
"Measles is highly contagious and the virus is spread easily from person to person through the air via sneezing or coughing," he said.
"We will be trying to contact people who we are aware have been in contact with the unwell person, however, because measles is an airborne disease anyone who was at the above listed locations at the times specified, should remain vigilant until July 17."
It was important anyone who suspected they may have the disease phone their GP or hospital first to avoid infecting anyone in the waiting rooms.