Health authorities overloaded by swine flu are also facing a whooping cough outbreak, after a surge in the number of diagnosed cases.
In Auckland, 92 people have been diagnosed with the disease already this year compared to 57 for the whole of 2008.
Waikato has seen 57 cases, compared with
85 last year, and Canterbury has had 145 cases, after just 15 for the first half of 2008.
Wellington Regional Public Health did not provide figures.
Waikato District Health Board medical officer of health Dr Anita Bell said the increase in her region was a concern, particularly because whooping cough, often known as the 100-day cough, could be fatal for babies.
About seven out of 10 babies who catch whooping cough when they are under six months old are hospitalised, and one in 30 of those babies die.
Babies who do not receive their immunisations on time are up to six times more likely to be hospitalised.
Auckland Regional Public Health Service clinical director Dr Julia Peters said it was crucial for parents to ensure their babies had all their whooping cough immunisations on time.
They should have their first jab at six weeks and booster shots at three and five months. Further booster shots should be given at ages four and 11.
Peters encouraged parents to take their children straight to their GP if they were having coughing fits that end with a "whooping" sound.
"They may be perfectly fine between fits, but when they have one it's nasty. They may struggle to breathe, vomit or even turn blue."
Peters said whooping cough was infectious for 14 days.
