BARRIE, ONT. -- Simcoe Muskoka residents hoping to get their second dose of a COVID-19 vaccine can book an appointment ahead of schedule after Ontario accelerated the program for the newly listed hot spot.

The Simcoe Muskoka District Health Unit (SMDHU) encourages residents to consider the Pfizer-BioNTech and Moderna shots "interchangeable" instead of waiting for a preferred vaccine.

On its Facebook page Monday, the SMDHU states, "Both Moderna and Pfizer use a similar mRNA technology, so the vaccines are interchangeable and safe to mix."

Ontario Medical Association's past president, Dr. Sohail Gandhi, said health authorities should have been upfront at the start of the vaccination process about not being able to approve mixing at that time because studies on it hadn't been completed.

"If that had been said right at the beginning, there wouldn't be some of the misinformation that's out there right now," Gandhi said. "You couldn't say that because it hadn't been studied."

The health unit notes that anyone who received AstraZeneca for their first dose can "safely get the AstraZeneca, Moderna or Pfizer for your second dose for strong protection."

Late last week, the province added Simcoe Muskoka to its list of Delta variant hot spots.

The region's associate medical officer of health, Dr. Colin Lee, explained the region falls into the top 10 of 34 health units across the province to have data showing 15 to 20 per cent of COVID-19 cases classify as the Delta variant making it a hot spot.

As of Friday, 18 cases had identified as the Delta B.1.617.2 variant across the region. Nearly 670 more screened positive for a variant of concern, requiring further testing to determine the strain.

Starting Monday, residents who had their first mRNA shot on or before May 9 can book or reschedule their second appointment through the provincial booking site.

Residents who received their first vaccine on or before May 30 can book their second shot starting Wednesday.

Complete information on Simcoe Muskoka's COVID-19 vaccination program, including how to book an appointment, is available here.