OTTAWA -- Eastern Ontario's top doctor suggests all residents of his region could receive the first shot of the COVID-19 vaccine within the next two to three months, as the guidelines change for administering the vaccine and more shipments arrive weekly.

"I would say probably May," said Dr. Paul Roumeliotis, medical officer of health with the Eastern Ontario Health Unit.

Dr. Roumeliotis made the comment just after Canada's National Advisory Committee on Immunization issued new guidance on administering the COVID-19 vaccine. The panel of medical experts says the second dose of COVID-19 vaccines can be given up to four months after the first.

"It's welcome news. I think the good news is that with studies that have gone subsequent to the release, both here and abroad, we now know the first dose will actually protect people for up to 16 weeks. We thought initially it was up to a couple of weeks, three-four weeks, and that's why the dosing schedule was initially 21 to 28 days," said Dr. Roumeliotis during an interview on CTV News at Five with Matt Skube.

"Now that we have it going up to 16 weeks, four months, it gives us a much more confidence in letting people you know wait a couple of months before they get the second dose. What it does it actually doubles our ability to vaccinate people with the first dose as soon as we get the vaccine supply in our hands."

On Wednesday, the first shipment of the Oxford-AstraZeneca vaccine arrived in Canada with 500,000 doses.

"This is a vaccine that is easier to distribute and less of a problem transporting it," said Dr. Roumeliotis, noting the vaccine will be administered to people between the ages of 60 and 64. "I do think it is a good population, I would have also wanted to look at perhaps people under the age of 64 that have chronic medical conditions as well."

The medical officer of health says with new shipments of Pfizer and Moderna expected to arrive, along with the AstraZeneca vaccines, the region will be able to speed up the timeline to vaccinate residents.

"I'm quite optimistic because I'm seeing the rate that which we'll be getting the vaccines and the fact that we'll be able to speed up the first dose because we're not worried about the second dose," said Dr. Roumeliotis.

"I'm optimistic that at least into the summer, things won't be back to normal, but there'll be more normal than previous years."