Epidemiologist Michael Baker says the Government and South Island leaders could and should have done more to keep COVID-19 out.
Two cases were reported in Christchurch on Thursday - both are unvaccinated. Despite the new cases, the city's been allowed to stay in alert level 2 for the time being.
The new cases are a couple who are both now in MIQ and nine of their close contacts are self-isolating.
Baker says leaders around the South Island have had different ideas about keeping COVID-19 out.
"I think there's been very mixed messages from leaders of South Island communities about the benefits of keeping the virus out of the South Island."
Christchurch isn't the first South Island city to have cases of COVID-19 during this outbreak - Blenheim reported one case on Saturday.
"There is no way of guaranteeing that we wouldn't see other cases pop up in other parts of the country," COVID-19 Response Minister Chris Hipkins says.
Westland Mayor Bruce Smith has been one southern leader outwardly calling for better protection of the South Island.
"We have been failed and there's no common sense with what's occurred today," he says.
There's also fury that the Government is mandating vaccines for the likes of sitting down at a cafe but not for those travelling out of COVID hotspots like Auckland.
"We should see more leadership from Air New Zealand because it's a health and safety issue for their staff and passengers on flights if they allow unvaccinated people," Baker says.
The Government says it's on their radar.
"One of the things that we'll be looking at, and we have been looking at, is whether there should be requirements for inter-regional travel for vaccination, particularly on flights. So we're working through the logistics of that," Hipkins says.
Air New Zealand wouldn't comment.
The National Party's COVID-19 response spokesperson Chris Bishop says the answer is full vaccination and rapid antigen tests for all travellers.
"That could potentially have prevented these travellers from going to the South Island and taking COVID," he says.
News of the positive cases caused those in Christchurch to rush to testing centres.
"I woke up real sick a couple of days ago. I wasn't going to do anything about it, wasn't going to do much about it, but then obviously hearing about the cases today sparks that kind of fear," one person tells Newshub.
It was the news many were expecting, but not welcoming.
"I just thought, 'what else can go wrong'," one says.
There's also widespread frustration that the two confirmed cases are unvaccinated and unwilling to use the COVID Tracer app.
"That was the shocking thing today to find out they're not using the QR codes," Christchurch Mayor Lianne Dalziel says.
While the city is remaining in level 2, there are so far 13 locations of interest in Christchurch.
