TORONTO -- Ontario health units said they needed more COVID-19 vaccines to keep up with a huge spike in demand as all adults across the province became eligible to book a shot on Tuesday.

Several said they rapidly ran out of appointments and urged residents to be patient as they awaited fresh supply.

"Eligibility has outpaced supply, and we simply do not have enough vaccines to keep up with demand," Ottawa Public Health wrote in a mid-morning tweet. "We acknowledge how frustrating this is. We anticipate more appointments will open when more vaccine becomes available."

The City of Hamilton also acknowledged residents' frustration as it said there were "limited or no appointments" at some mass clinics. The health unit for Kingston, Ont., reported a similar situation.

In London, Ont., the region's top doctor said his health unit would have 24,000 doses for a population more than five times that size.

"I'm sorry in advance for the frustrating situation of limited vaccine supply," Dr. Chris Mackie wrote on social media Monday night.

Jenna Hope, 30, said she managed to get a mid-June appointment through the Middlesex-London Health Unit's online portal after waiting nearly an hour and a half in the queue.

"When I first joined the queue there were 3000+ appointments available and by the time I was able to book mine there were about 800 left," she said in a message.

Others on social media expressed frustration at being told after a long wait that shots were used up or not available until at least a month later.

The government said more than 252,000 vaccine appointments were booked through its online portal and call centre by 3 p.m. Tuesday, although a spokeswoman for the premier's office said those were split between first and second-dose bookings.

Health Minister Christine Elliott brushed off criticism that the province had expanded eligibility too fast, saying an initial rush of bookings and long waits were seen every time the government opened appointments to more residents.

"It's probably just part of that normal crush that you see when we open a new age band," Elliott said. "It's good news, in the sense that people are anxious to receive the vaccine."

Elliott said incoming vaccine shipments will allow more people to book appointments soon.

The province was initially supposed to expand vaccine eligibility only to those aged 30 and older this week but said Monday that an early vaccine shipment allowed it to open shots everyone aged 18 and older. At the same time, it reverted to allocating vaccines on a per capita basis following two weeks of sending half its supply to hot spots.

NDP Leader Andrea Horwath said the government must give local health units the appropriate resources to speed up local vaccination efforts, including funding to run sites around the clock.

"The government needs to step up," she said.

Liberal House Leader John Fraser said public health units were not given advance notice of the change in eligibility criteria so they had no time to prepare for the influx of people trying to book shots Tuesday.

"That's not good planning and and it's causing a lot of frustration," he said.

Ontario's vaccine effort had been criticized initially for a slow and bumpy start. The rollout ramped up in recent weeks and the government has said it aims to have all eligible adults fully vaccinated by the end of September.

The province has also said it plans to start vaccinating children aged 12 and older with the Pfizer-BioNTech shot from May 31 onwards. Lambton Public Health said Tuesday, however, that it would start taking vaccine appointments for youth aged 12 and older and encouraged families to get vaccinated together.

Tuesday's immunization expansion came as the province's daily cases continued to decline. Ontario reported 1,616 new cases of COVID-19 Tuesday and 17 more deaths. The data was based on over 22,900 completed tests.

The Ministry of Health said there were 1,484 people are in hospital with the virus, including 764 in intensive care.

The province remains under a stay-at-home order but Elliott said Tuesday that the government was developing an economic reopening plan that would be released "very soon."

"It's also sector-specific, looking at what different types of sectors (can) perhaps be reopened, and what their specific needs and timelines are as well," she said.

A spokeswoman for Premier Doug Ford said Ontario will not return to the tiered colour-coded restrictions system it used before imposing the stay-at-home order.

The currently set to expire June 2 has, among other things, forced the closure of outdoor recreational facilities - a measure that's been heavily criticized.

A coalition of athletic associations wrote Ford on Tuesday, urging his government to reconsider the ban on many outdoor sports and activities. It said sports like golf, tennis, and volleyball can be played safely outdoors with little risk of COVID-19 transmission.

"Please consider the facts before you, and the health and well-being of all Ontarians as we work through this pandemic together," they said.

This report by The Canadian Press was first published May 18, 2021.