Director General of Health Ashley Bloomfield says it is inevitable new Covid-19 variants - such as the newly-discovered XE strain - will arrive in the country.
Early studies of the new variant, which has spread in the UK, shows it to be more transmissable than Omicron. It's level of severity is still to be assessed.
Dr Bloomfield told Morning Report earlier wider genomic sequencing will be introduced as the country moves down its security settings.
Dr Bloomfield said although Covid-19 case numbers are falling, the pressure on the health system isn't.
Cabinet has decided to keep red restrictions in place, and will review them again next week.
Dr Bloomfield said the Omicron outbreak is still large, with thousands of cases, including more than 700 in hospital.
He said people can be assured that the measures mean it's safe to go out and about.