TORONTO -- As the Brampton Civic Hospital celebrated zero COVID-19 patients in critical care Wednesday, for the first time since the start of the pandemic, the Ontario Hospital Association (OHA) warned that an impending surge in virus case counts could represent a threat to the province.

“This pandemic is ending but a fourth wave could still inflict a deadly toll on the unvaccinated,” OHA president Anthony Dale said in a statement.

The association called on Ontarians who had not yet received two doses to get fully immunized before an anticipated autumn increase in case counts—in what is now being called the pandemic of the unvaccinated.

“I think it’s going to be primarily be younger unvaccinated children [affected], and of course the adults who have chosen not to get the vaccine,” York Region emergency physician Dr. Steve Flindall said of a fourth wave.

“I’m really hoping the vaccinated individuals in the population will act as a firebreak between transmissions.”

Many experts remain optimistic that Ontario’s health-care systems will not succumb to the same strain as during the third wave of the virus, when non-urgent surgeries had to be postponed and patients were transferred between hospitals to access critical care.

“The risk of being on the brink of collapse of the hospital and health-care system, like we were in April—I don’t think that we should see that, or expect that, in the coming months because of the vaccine rate that we have here in Ontario,” said Dr. Dale Kalina, medical director of infection and control at Joseph Brant Hospital.

Kalina pointed to the recent spikes in COVID-19 cases in the U.K. and the U.S.; in the U.K., where the vaccination rate is comparable to Ontario’s, the increase in COVID-19 hospitalizations was minimal. But in Florida, where only 59 per cent of adults are fully vaccinated, hospitalizations increased Tuesday to a level that surpassed the record set before vaccines were even available.

“We’re running out of materials, our staff is exhausted, we’re really really straining,” Florida infectious disease specialist Dr. Aileen Marty told CTV News Wednesday.

“It’s particularly distressing that so many of our patients are young, otherwise healthy individuals that can’t breathe.”

“Given that thousands of Ontario children under the age of 12 will be returning to indoor in-person learning in just a few weeks, it's vital that all eligible residents receive both shots to keep transmission levels low, protect vulnerable populations and ensure that access to non-COVID related hospital services is not disrupted a further time,” said Dale.