KITCHENER -- At least three pharmacies located in Waterloo Region will likely receive their first doses of the AstraZeneca vaccine this week, provincial officials said Tuesday.

Solicitor General Sylvia Jones said there are plans to expand the pharmacy vaccination program to another 300 locations this week, with at least three locations in each health unit.

"We don't have the vaccine yet, but the pharmacies are lined up," Jones told reporters at the press conference. "As we continue to see expansions of the AstraZeneca vaccine, then we will continue to expand the pharmacy rollout. But, we have a lot of pharmacies who are very excited and are looking forward to offering that AstraZeneca to their patients."

Dr. Kelly Grindrod, an associate professor at the University of Waterloo's School of Pharmacy, said the locations haven't been confirmed to the public yet. However, she said the pharmacies are likely already working on training on how to administer the vaccine.

"As a part of this role, they have to get up and running as well," Grindrod said.

According to Grindrod, expanding the pharmacy program is all dependent on how much vaccine is available.

"Supply will probably, in some part, dictate how many pharmacies on the potential list of pharmacies in Waterloo Region will actually get the vaccine or not," she said.

Grindrod said supply will likely be directed to COVID-19 hotspots in the area.

"Pharmacies are being chosen across the province to match areas that need the vaccine," Grindrod said. "Areas where there's more cases and areas of concern will hopefully see the first pharmacies on the list that get supply will be in those areas that need it the most."

Pharmacies in Toronto started administering COVID-19 vaccines in Toronto as part of a pilot program earlier this month. Grindrod said the pilot didn't include pharmacies in high-risk areas.

"That was a lesson learned in the pilot that seems to be addressed in this next phase," she said. "They'll find pharmacies or start with pharmacies that are in some of the highest-need areas for vaccines."

Ontario has followed national guidance on the AstraZeneca vaccine, pausing use in people under the age of 55.

"This is an abundance of caution," Grindrod said. "We haven't had any of these cases in Canada in people who have had this vaccine."

Earlier this year, officials only offered AstraZeneca to people between the ages of 60 and 64. Grindrod said early research hadn't tested the vaccine on older people, but Canada approved use in people over the age of 65 earlier this month.

Grindrod said all vaccines approved for use in Canada, including AstraZeneca, are very effective at preventing serious illness, hospitalization and death.

Grindrod also said tension over vaccine distribution will likely only be solved as more supply becomes available in Ontario and across Canada.

"We have struggled to get vaccine," she said. "We're finally getting it now, but when you start getting into not enough and spreading it out, no matter what, it's never going to seem fair."

On Tuesday, Waterloo Region health officials said people between the ages of 60 and 69 can now pre-register for a vaccine.

The vaccine task force said more than 10 per cent of the population has received at least one dose of a COVID-19 vaccine.

With reporting by CTV News Kitchener's Nicole Lampa