The Ministry of Health says more draconian border controls could be needed if swine flu returns in a second wave.
The number of those seeing a doctor for flu has dropped slightly in the latest week for which details are available, but officials say it's too early to know whether flu has peaked.
The 1918 Spanish flu pandemic returned in a more virulent second wave.
National pandemic co-ordinator Steve Brazier says planning is already underway for the possibility that this could happen again. A special focus is being placed on border control.
Meanwhile, Health Minister Tony Ryall says experience gained from responding to swine flu means New Zealand will be much better placed to handle a more severe flu pandemic in future.
He says swine flu has been milder so far than the ministry had in mind when New Zealand's flu pandemic plans were designed.
Listen to Insight on the Radio New Zealand website for more about flu.