The number of Ontario schools that are closed due to COVID-19 outbreaks or operational considerations related to the pandemic has risen again and Ontario's top public health official is warning that we will "sadly see increases cases in school settings" in the weeks and months ahead.

The Ministry of Education says that there are now 16 Ontario schools that have been switched to remote learning, up from 15 one day prior.

It is the highest that number has been at any point this school year and represents a significant increase from this time last week when just five schools were closed.

Three of the shuttered schools are located in Toronto, including Grenoble Public School, which was ordered to close earlier this week after at least 15 students tested positive for COVID-19.

"This is the time of year where we expect an increase (in cases) and sadly yes we'll see increased cases in school settings, especially the elementary level where they haven't had the benefit of vaccine," chief Medical Officer of Health Dr. Kieran Moore said during a briefing on Thursday afternoon.

"The silver lining, though, is that we now have the vaccine (for children aged five to 11). So for parents, I think one of the key motivators to get your child vaccinated is the decrease in risk amongst at the school setting, the social setting or in the home setting because the vaccine is very powerful at preventing infection, around 90.7 per cent protection against symptomatic COVID-19 in the randomized clinical control trials. That's just a brilliant level of protection."

School-related cases of COVID-19 declined steadily through most of October but have now been on the rise for several weeks, outpacing the increase in infections in the broader community.

According to the latest data released by the Ministry of Education, there were 154 new instances of COVID-19 in public school students and staff confirmed over a 24-hour period ending Wednesday afternoon.

That is up from 129 cases over the same time period last week.

The number of active cases associated with the public school system is up 24 per cent over the last week and now stands at 1,489.

As a point of comparison, Ontario's active caseload is only up 14 per cent over the same time period.

During Question Period at Queen's Park on Thursday, NDP MPP Rima Berns‑McGown said that parents are now watching the numbers "nervously" because "the last time we saw numbers spike like this, the province's cancelling of in-person classes wasn't too far behind."

Moore, however, told reporters on Thursday afternoon that the arrival of pediatric vaccines for school-aged children "should help limit the spread in the elementary school settings" and ultimately help to ensure that in-person learning can continue to be offered.

"First doses will be helpful and second doses will be tremendously beneficial against Delta on limiting the spread. So there is hope. I know this is a difficult time. But there's a hope now that we have the vaccine that we can have decreasing impact on our elementary school system," he said.

Since the beginning of the school year, there have been 6,945 confirmed cases of COVID-19 linked to schools. During the 2020-2021 school year, it took until Dec. 17 to surpass that number.

The number of school closures is also well ahead of where it was at this point in 2020, when just four schools had been switched to remote learning. That number, however, rose to 22 by the December holiday break.