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The Otago University professor says the extended alert level changes across the country were the right thing to do in these circumstances.
While it was not necessary to find the source of the cluster in order to control it, it would be critical to do so to stop any future possible breaches, Sir David said.
"I agree with the those who say the virus hasn't been lurking around for the last three months or longer. This virus has undoubtedly come in through the border, one way or another, and we need to discover how that happened."
He told Kim Hill that New Zealanders have to learn to cope with outbreaks without going into lockdown.
"Places like Taiwan have done extremely well without lockdowns. We need to get ourselves organised so that we don't have to have a lockdown when this happens again.
"I mean this virus is going to be around for several years. We've had a wonderful three months with a light of near normality. But I think we must expect there will be failures of excluding it again."
Weeks ago, he was asked to be an advisor on a select committee in the UK's House of Commons, he said. On that venture, he was joined by two other experts, one of whom was a professor in Hong Kong and had been involved in controlling the SARS pandemic.
Sir David had heard the Hong Kong professor say there are three essential components to dealing with these pandemics and they were physical distancing, including mass masking, testing and rapid contact tracing, and border controls.
"And he said if you relax any one of those three, you better make sure you really tighten the other two. Now we didn't just relax physical [distancing], we basically just stopped it under alert level 1 ... and I think there are some sensible things we can be changing while this virus is around.
"Far from actually making our testing more rigorous, we basically got quite slack about that and clearly we've also had systemic problems with our border.
"Those are the lessons we have to learn and in future, we don't just have to have a really good testing strategy, we also need to try and find ways to augment rapid contact tracing and that's where the possibility of using something like the CovidCard have to be considered a lot more quickly than has been done so far."