Health officials believe swine flu has affected up to a quarter of New Zealanders, and many others could be vulnerable to a predicted second wave of infections.
British health authorities say a second wave may have already begun there, while Australia is poised to begin a vaccination programme.
The Ministry of Health estimates that between 11% and 25% of New Zealanders have had swine flu and would be immune in any second wave.
To confirm the figures, the ministry will to carry out a survey, which involves medical researchers taking blood from a random sample of people.
The Government is expected to receive recommendations soon on a vaccination programme, and the survey results would be used to help target the vaccine.