In the seven days to November 19, 7881 new cases were reported, up by almost 2000 on the previous week.
Baker told Morning Report uptake of boosters had slowed, and people often did not know whether they were eligible.
"Anyone over 30 can get a booster at this stage if it's over six months since their last dose or last Covid infection," the University of Otago public health professor said.
Boosters were particularly vital for those aged over 75, Māori and Pasifika over 65 or people with underlying health conditions, Baker said.
Of people aged 50 to 64, fewer than 40 percent had received their second booster.
Part of the reason for the low rates was people becoming accustomed to living with the virus, Baker said.
"It's really our biggest infectious disease problem still.
"If people are not getting their boosters, they're far more likely to go to hospital and that's going to put more pressure on the health system, so yes, it's essential."
Baker wanted to see more awareness raised about booster eligibility by Te Whatu Ora and the Ministry of Health.
Wastewater testing had indicated the country was seeing a peak Covid-19, with the highest number of cases since January.
And it may be a recurring trend, Baker said.
"We expected that these waves would get smaller over time but now we're seeing the second wave for this year of a similar size [to the first in 2023], so this may be the reality of this virus.
"Every time you are infected and re-infected, you run all of these additional risks, and we are worried about the mounting burden of long Covid. This is different from the way say influenza pandemics behave," he said.
"So I do think as a society, we need to be taking a lot more precautions to decrease the risk of catching this virus over and over again."