Epidemiologist Michael Baker says his biggest concern is that the spread of Delta is an "outbreak of the unvaccinated".
Auckland has now been living with tough restrictions for two months.
Asked why the city is still experiencing so many cases (57 today) Professor Baker said "lockdown fatigue" is undoubtedly a factor.
"We hear a lot of anecdotal reports of that. Also, the rules were relaxed a bit in terms of more social gathering outdoors and outdoor gatherings on the face of it should be relatively low risk because there's better ventilation, but of course, it does provide more opportunities for mixing and they may turn into indoor parties and so on.
"So I think we are seeing those effects."
He said on the plus side, as the number of people vaccinated increased, the reproduction number would decrease, however, the outbreak could still get out of control, hurting Māori and Pasifika in particular.
"The unvaccinated are increasingly Māori and Pacific people. So we do run the risk of this becoming a very unequal outbreak, and I think that's a really critical factor that Government needs to look at, at the moment."
Professor Baker also said a level 4 lockdown may still be necessary, depending on the outbreak's movement.
"I don't think that we can rule out the need for some kind of circuit breaker lockdown in the future, but at the moment, it looks like the system is managing these numbers."
He said if the country can reach 90 percent vaccination coverage, it would be reasonable to move to level 2.
He said Auckland's border could be dropped by Christmas "potentially" if there is uniformly high vaccine coverage across Aotearoa.
"This is where I think we could definitely move down to alert level 2, which actually puts very few barriers in the way of the virus, in practice, and in addition, we could have the schools open again. So I think that would be a good point to make that move."
But it is critical that high vaccination coverage includes Māori and Pasifika demographics, for dropping the border to be safe, he said.