New Zealand's coronavirus cases have jumped, as questions grow about the government's response to the pandemic given the slowest vaccination rate among developed countries and the economic pressures of prolonged isolation.

Eleven new cases have been reported, taking the total to 21 in the latest outbreak that ended the country's six month, virus-free run.

Only about 23 per cent of New Zealand's five million people have been fully vaccinated so far, the lowest rate among the 38 members of the Organisation for Economic Co-operation and Development.

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