TORONTO -- Demand for the flu shot soared this week as the second wave of the coronavirus pandemic intensified across the country.

Following warnings that a “twindemic” of influenza and COVID-19 this fall could overwhelm hospitals, researchers had reported that more Canadians than normal were likely to seek out influenza immunization. The Public Health Agency of Canada said more than 13 million doses were ordered this year, compared to 11.2 million in 2019.

But as the flu shot became available in Ontario this week, pharmacies were already feeling the pinch. At his two Shoppers Drug Mart locations in the west end of Ottawa, pharmacist and owner Jordan Clark said it’s been an “all hands on deck situation.” Between his two locations, Clark says he and staff have already administered about 1,000 flu shots since Tuesday.

“It’s been a hectic week,” he told CTVNews.ca over the phone on Friday. “In my one store, the demand has been much, much higher than we anticipated. We definitely had to make some adjustments on the fly.”

He added additional pharmacists to give flu shots, with a total of four people administering the vaccines at any given time, he said, and was forced to pull staff from the front of the store to monitor lineups.

Though some Shoppers Drug Mart locations and other pharmacies were out of stock in less than 24 hours, others remain stocked and have continued to be replenished throughout the week. In previous years, pharmacies might need to be restocked once every week or two, but this season has already proven different.

Pharmacies in B.C. experienced the same rush this week. Although many pharmacies are asking customers to book ahead online, most appointments in the Vancouver area have been booked.

“It’s just been non-stop, which is great,” Victor Chu, the owner of the Pharmasave in Vancouver’s Bentall Centre, told CTV Vancouver. “I’m getting people I don’t normally see for flu shots coming in, so the uptake is amazing.”

Though Chu has "plenty" of vaccines for now, he worried that the uptick may lead to a shortage in time. B.C. ordered an additional 450,000 doses of the flu vaccination this year and, although officials have maintained there will be enough to go around, they note seniors and those with underlying health conditions should be given first dibs.

Alberta ordered 1.96 million doses of the vaccine this year, a record for the province and more than 20 per cent compared to last year.

Vulnerable Albertans are already able to get their flu shot; however, the rest of the population will have to wait until Oct. 19.

"Most pharmacies are planning for an appointment-based process, which is very different from previous years," Matt Tachuk with the Alberta Pharmacists Association, told CTV Edmonton.

“They’re confident that they’re going to have sufficient vaccine to supply the entire flu season,” said Clark. “But because the demand is so front-loaded, there may be gaps in some days where stores do run out but then are being supplied shortly there after.”

Nationally, the Public Health Agency of Canada (PHAC) assists in co-ordinating and overseeing the distribution of the flu vaccine for public programs, along with Public Services and Procurement Canada (PSPC), Health Canada, vaccine manufacturers, and provincial or territorial partners.

"PHAC does not decide how much vaccine provincial and territorial governments purchase for their populations; this decision is made by each provincial and territorial government based on past experience, the influenza season forecast, and the requirements of its immunization program," a PHAC spokesperson told CTVNews.ca.

This year, officials factored in the expectation that demand would spike during the pandemic, but it wasn’t enough for some pharmacies, even this early in the season.

“Some stores are just seeing truly unprecedented numbers within the first week,” Clark said.

Ontario pharmacists have been reassured by the Ministry of Health, which provides the flu shots, that the supply will not run out and is merely “front-loaded” at the moment. The province ordered 5.1 million flu vaccine doses this year, or 700,000 more shots than were used in 2019, including 1.3 million "high-dose" vaccines for seniors. Distribution began in late September, first to public health units, long-term care homes, and hospitals. "Broader community distribution," including to family doctors and pharmacies, is expected to continue for the "coming weeks," the Ministry of Health said in an email. "Following initial shipments from distributors, orders will be made as the provincial supply is replenished from the shipments from vaccine manufacturers," a spokesperson wrote. "The province will explore the purchase of additional doses as required."

PHAC notes that, to meet the increase in demand this year, a small portion of Canada’s vaccines will also be supplied in November and December.

"At the present time, no supply issues are expected this year and the increased demand by provinces and territories that has occurred since orders were first placed with suppliers in February is expected to be met in full," the PHAC spokesperson noted.

The demand for the flu shot has been anticipated for months. In September, a group of Ontario pediatricians warned of a “potentially devastating collision course” ahead of flu season if the government didn’t develop a mass immunization strategy. Toronto pediatric emergency physician Dr. Dina Kulik told CTVNews.ca last month that this could be drive-thru options like what has been seen at some COVID-19 testing clinics and “outdoor tents set up where kids can go through one at a time.”

Some doctors, including at least one in New Brunswick, are already hosting outdoor flu clinics in parking lots, while others are considering drive-thru clinics. Even without tents and outdoor options, the flu shot process is different in 2020 than in year’s past, not only for increased COVID-19 safety protocols, including mandatory masking indoors, physical distancing and hand sanitizing stations. Many pharmacies are encouraging customers to fill out registration forms online to curb wait times in the store.​

- With files from CTV Vancouver and CTV Edmonton