TORONTO - Mayors representing the majority of Ontarians are pushing the province to establish a vaccine certification system as a top science adviser says that without one, the Delta variant may overwhelm the health-care system.

TORONTO - Mayors representing the majority of Ontarians are pushing the province to establish a vaccine certification system as a top science adviser says that without one, the Delta variant may overwhelm the health-care system.

The Ontario Public School Boards' Association, meanwhile, urged mandatory vaccinations in schools in order to keep them as safe as possible.

Premier Doug Ford has so far refused to mandate vaccines in any setting, saying he doesn't want to have a split society.

Ontario's Big City Mayors joined a chorus of voices in both the business and medical communities calling for proof of vaccination to access non-essential services. They believe such a system could help mitigate a fourth wave of COVID-19.

"The faster we can enact a proof of vaccination system, the faster we can protect more Ontarians from the effects of the Delta variant," said Jeff Lehman, chair of the group and the mayor of Barrie.

Dr. Peter Juni, the scientific director of the province's science table, said vaccine certificates would keep high-risk – unvaccinated – people out of high-transmission settings such as restaurants, bars and gyms.

"There is no way we’ll be able to keep this Delta variant under control in high-risk settings … if we do not have a distinction between fully vaccinated and the rest of the population," Juni said. "It's just not possible. Delta is too transmissible."

Cases in Ontario are already doubling every 10 days, Juni said, and it's not the time to ease restrictions any further.

"I can't see this happening if it continues at these levels," he said. "There’s just too many unvaccinated people out there that will bring the health-care system at an edge."

Ontario has said that the province can move beyond the current Step 3 of its reopening plan and see the majority of restrictions lifted if 80 per cent of people 12 and older have at least one dose of a COVID-19 vaccine, 75 per cent of them have both doses, and no public health unit has less than 70 per cent of eligible people fully vaccinated.

More than 81 per cent already have at least one dose, with nearly 73 per cent fully vaccinated. Seven of the province's 34 health units are still under the 70 per cent target, though most are just a hair away.

"We will continue to monitor data to determine when it is safe to exit the roadmap and lift the majority of public health and workplace safety measures currently in place," a spokeswoman for the health minister said in a statement.

But Juni said the Delta variant has moved the goalposts.

"The concept of herd immunity has become obsolete with the Delta variant," he said.

When the Alpha variant was dominant, unvaccinated people could have been protected with enough vaccinated people - not so with Delta, Juni said. The vaccines are good but not perfect, and have a lower effectiveness with Delta, he said.

"A slight decrease in effectiveness against infection means that these (unvaccinated) people will eventually get infected," Juni said.

Unvaccinated people have a more than 20-fold increased risk of ending up in intensive care, he said.

"This should really be a wakeup call for all those out there who are still contemplating or hesitant…especially people above the age of 50," Juni said.

"They’re starting to play Russian roulette."

People aged 50 and up are at a higher risk of severe illness, and about 83 per cent of those aged 50 to 59 have had at least one dose. With current rates increasing by 0.3 percentage points per week, Juni estimates it could take 20 more weeks "if everything goes well" to hit 90 per cent.

At that point the burden on the health-care system would be reduced considerably, but the pandemic will not be over, Juni warned.

"The pandemic will only come to an end when nearly 95 per cent of the population, including small children, are either immune through vaccination or immune through infection."

Ontario reported 510 new cases of COVID-19 Friday, with more than 80 per cent in people who are unvaccinated or partially vaccinated.

There are 111 people in intensive care units due to COVID and Health Minister Christine Elliott said just three are fully vaccinated, though the vaccination status isn't known for about half of the patients.

Friday's new cases are based on more than 23,500 tests completed in the previous day. More than half of them are in people aged 20 to 39.

This report by The Canadian Press was first published Aug. 13, 2021.