Ontarians will be able to get fully vaccinated against COVID-19 sooner than expected as the province shortens the interval between doses.

The move announced Friday is part of the government's plan to fully immunize all willing adults by the end of August now that Ontario has a steady vaccine supply and 65 per cent of all adults have a first shot.

Shortened dose intervals will be offered first to those aged 80 and older next week, followed by those 70 and older in mid June. Residents will then become eligible for faster second doses based on when they received their first shot.

The onus to book earlier second doses rests with individuals, with no provincial plan to contact recipients directly to move up appointments. Residents will keep their original second-dose appointments – four months from the first – if they don't book an earlier shot.

Premier Doug Ford said getting more people fully vaccinated is essential to beating COVID-19.

"The faster we deliver vaccines, the faster we can put this pandemic behind us for good," he said. "Based on what we know about upcoming shipments, everyone in Ontario who wants a vaccine could be fully vaccinated by the end of August."

The second-dose schedule could move faster if supply increases, Ford said.

The booking process for first shots was challenging for many, as people reported technical barriers and issues trying to navigate various systems to find appointments. Vaccinations have been offered at locations that include mass sites, hospitals, pharmacies, doctors' offices and pop-up clinics.

The province's health minister expressed confidence on Friday that seniors would be able to move up their second appointments if desired.

"We didn't have a problem with people 80 plus getting their first doses organized, and we're sure that their second doses won't be a problem either," Christine Elliott said.

The shortened interval could be as small as 28 days for the Pfizer-BioNTech and Moderna vaccines in the coming months, depending on supply.

Those who got a first shot of the Oxford-AstraZeneca vaccine will be offered a second dose after 12 weeks, though it could be a different vaccine depending on awaited federal guidance. A recent U.K. study found giving second doses of AstraZeneca vaccine at 12 weeks or later was more effective against COVID-19 than taking shots six weeks apart.

Those between the ages of 12 and 25 will become eligible for second doses in early August.

The province plans to give first doses to the majority of youth aged 12 to 17 next month and administer their second doses in August so that as many as possible will be fully vaccinated by the start of the school year.

Vaccination teams also plan to start offering shots to youth in 31 fly-in First Nations communities and Moosonee in northern Ontario starting Monday.

The acceleration of the vaccine effort comes as COVID-19 cases and hospitalizations have been dropping in Ontario in recent weeks. The province remains under a stay-at-home order imposed to battle a devastating third wave and schools continue to teach students online.

The province's three-step reopening plan, which is set to begin the week of June 14, is dependent on vaccination rates and other health indicators.

Ford indicated on Friday that he will stick to that plan, even as vaccinations increase and cases decline.

"It kills me to keep these businesses closed, but I have to, for the long-term, protect everyone's health," he said. "We're going to open up cautiously and carefully... because I do not want to happen, what happened before and all of a sudden, the cases go up."

Ontario reported 1,273 new cases of COVID-19 on Friday and 14 more deaths linked to the virus. The data is based on nearly 40,900 completed tests.

The Ministry of Health reported 1,023 people in hospital, including 645 in intensive care and 458 on ventilators.