TORONTO — If Ontarians wear masks indoors for another few weeks a "tidal wave" of COVID-19 cases could quickly recede, a top scientific adviser said Thursday, as the health minister insisted a mandate was unnecessary. 

Dr. Peter Juni of the province's COVID-19 science advisory table said wastewater monitoring suggests the province is seeing between 100,000 and 120,000 new cases of the virus each day, in part because so many people stopped wearing face coverings when the mandates lifted last month.

"We are creating a tidal wave again," Juni said. 

"If we had consistent communication ... recommending that it would be really important right now for everybody to wear masks indoors again, coming from all sides, including the province, this would help."

The six-figure case counts are a far cry from the 4,224 officially reported Thursday due to limits on PCR testing. 

Juni said the restricted eligibility for the tests means it's unclear how long this wave will last, because it's not known how many people have been infected so far and have an extra bit of immunity. 

He said getting a third dose of a COVID-19 vaccine is even more effective at boosting immunity than catching the virus, as evidence suggests the current variant can be caught multiple times. 

Juni said the government should be more clear about the benefit of that third dose, and stop suggesting that it only takes two to be "fully vaccinated."

He urged the government to adopt a few simple messages: "This is a three-dose vaccine, get your third dose. We have lifted the mask mandates but we'll continue to strongly recommend, given the epidemiological situation, that people mask up right now just for a few more weeks.

"If we have clear communication, going through all channels in this direction it will help. People will be less confused in these confusing times," he said.

His comments came as all three opposition parties called on the government to reinstate or continue several public health measures, including mandatory masking, in order to blunt the sixth wave of COVID-19. 

But Ontario Health Minister Christine Elliott, citing the province's chief medical officer of health, Dr. Kieran Moore, said the province need not reintroduce mask mandates because a rise in cases was expected. 

"As Dr. Moore himself has said, we should not be surprised to see an increase in the number of cases that we’re seeing in Ontario because we have released a number of the public health measures and we have a more transmissible variant, but vaccination is the key to success," Elliott said in the legislature Thursday. 

Moore held his last public briefing on March 9 and has turned down interview requests since then. At the time of that press conference, 751 people were hospitalized with COVID-19, compared to 1,126 on Thursday.

"Dr. Moore has chosen not to appear in regular conferences because, in his words, we have to learn to live with COVID as it is now," Elliott said. 

"We can’t continue to have to need weekly updates when we know that we are seeing an increase but the increase is manageable." 

But Liberal House leader John Fraser said Ontarians have relied on the top doctor's briefings to determine their risk of catching COVID-19. 

"Now we’re facing what looks like it’s going to be the biggest wave and there’s a vacuum, a vacuum of leadership. The chief medical officer of health is nowhere to be found," he told the legislature.

Meanwhile, Ontarians aged 60 and older were able to start booking appointments for a fourth dose of a COVID-19 vaccine Thursday. 

First Nations, Inuit and Métis individuals and their non-Indigenous household members aged 18 and above are also eligible to start booking those shots.

Fourth doses are being offered at a recommended interval of five months after the initial booster shot.

Residents can book appointments through the provincial vaccine portal, public health units with separate booking systems, Indigenous-led vaccination clinics and some pharmacies.

Fourth doses are already available to long-term care and retirement home residents and immunocompromised people in Ontario.

This report by The Canadian Press was first published April 7, 2022.

Nicole Thompson, The Canadian Press