Epidemiologist professor Michael Baker says the Government should consider putting Southern Africa on its very high risk travel list, following the discovery of a new variant of Covid-19.
The World Health Organization has named the B.1.1.529 Covid variant "Omicron" and an advisory group has said it should be designated as "of concern".
In a statement, the WHO said preliminary evidence suggests the latest variant carries a "higher risk of re-infection than other variants of concern".
New Zealand's "very high risk" list means travel from those countries is temporarily restricted to citizens, their partners and children, and parents of children who are citizens.
Other travellers, including New Zealand residents, can enter only if they spend 14 days outside a very high-risk country before their arrival here.
Baker told the Herald the Government should consider adding Southern Africa to the list to turn up its Covid-19 response if needed.
"I'm sure the actual number of travellers to New Zealand from those countries is probably tiny.
"I think it would probably be relatively easy to put those countries in the same grouping as Papua New Guinea (already on the list) as the highest risk and that does give you extra precautions."
Baker said he understood the new variant was worrying for people.
"The best laid plans can get upset by what the virus does. I hope it won't be the case.
"If this turns out to be a real threat to the effectiveness of vaccines, which is the main worry, then this might mean we have to review our plans for January and February next year on relying on home isolation entirely.
"But look, that's really leaping ahead, it's important not to catastrophize and we need to wait for more information."
Baker also noted New Zealand was among a minority of countries which still managed their borders tightly, with layers of protection like pre-travel testing and quarantine.
"It means we're in a completely different situation compared to the rest of the world. We can keep this virus out if we need to."
A spokesperson for Covid-19 Response Minister Chris Hipkins said they were monitoring the situation.
The Ministry of Health has been approached for comment.