WATERLOO -- Moving to Step 3 on Friday will "increase the risk of spread" of the COVID-19 Delta variant, Waterloo Region's top public health doctor warns.

Speaking at a Region of Waterloo board of health meeting on Wednesday, Dr. Hsiu-Li Wang said although the area’s COVID-19 trends are moving in the right direction, the Delta variant "continues to circulate in our community and remains a threat."

She's urging residents to continue to follow public health guidelines, like physical distancing and mask-wearing, and to avoid crowds, closed spaces and areas with poor ventilation.

"It is important we do not let up now," she said. "At an individual level, be cautious as you add activities for yourself and your family."

Waterloo Region, along with the rest of the province, will enter Step 3 on Friday. The third stage of Ontario's Roadmap to Reopening allows for indoor dining and fitness to resume, larger social gatherings and for movie theatres to reopen, among other loosened restrictions.

"We can expect that the risk of Delta spread will increase," Dr. Wang said. "This is why we must continue getting vaccinated as quickly as we can, and we must continue to practice public health measures diligently."

In recent weeks, the vaccine rollout in Waterloo Region has ramped up. More than 80 per cent of adults have now received one dose, while more than 54 per cent are fully vaccinated.

Health officials in the region are urging residents to move up their second dose appointment.

Meanwhile, local hospitalizations and intensive care unit admissions have slowed.

"Our public health and health care indicators continue to improve or stabilize, and our vaccination rates have increased rapidly," Dr. Wang said. "Weekly incidence rates back to those in March, prior to the third wave."

Ontario will not leave Step 3 until 80 per cent of those 12 and older have received one dose and 75 per cent are fully immunized.

Another caveat to moving to the next phase is that no single public health unit can have less than 70 per cent of its eligible population vaccinated.

Tuesday, Ontario's chief medical officer of health Dr. Keiran Moore, said he believes a rise in COVID-19 cases is likely in September.

Dr. Wang responded to those concerns on Wednesday, saying she feels a potential fourth wave could be blunted if enough people are vaccinated and public health protocols are followed.

"Any time you have more social contacts and less restrictions, like when we advance in the reopening phases, and also when you start to get into seasons of the year when people spend more time indoors, you always have a greater risk," she said. "But a greater risk doesn’t have to amount to a real surge or a real significant impact to our community, to our healthcare system, if we can control it. The best way to control it is through vaccination."