Clinical Associate Professor, Lance Jennings, said he was concerned the virus was still circulating in some communities throughout the country.
"At this time control is only possible through social distancing and hand washing."
Jennings said people may interpret Monday's direction “to prepare to move to Level 3” as a time to relax.
"We do not fully understand the nature of this virus and the importance of each potential route of transmission from person to person," Jennings said.
On the first day the lockdown was lifted, a large crowd gathered outside a BurgerFuel in Auckland. They did not observe social distancing regulations.
"I am also concerned when politicians demonstrate that they do not understand the seriousness of the COVID-19 disease and the SARS-CoV-2 virus that we are attempting to control," he said.
Jennings said a second wave was a real risk, but as an island nation it would be easier to manage the country's borders.