Yes, in rare cases, you can get sick with COVID-19 after your first shot, Ontario doctors say

Even though 40 per cent of Ontarians have received at least one dose of a COVID-19 vaccine, doctors warn that in rare cases people can still set sick while waiting for the second dose and need to continue to take precautions.

Those on the frontlines say the recent uptick in vaccinations will help quell Ontario's third wave, but warn a single shot is not a silver bullet.

Some of the province’s top infectious disease specialists say, anecdotally, they have seen patients come through their hospitals after getting their first dose of a COVID-19 vaccine.

The Public Health Agency of Canada says roughly 1.3 per cent of Canadians have contracted COVID-19 after receiving their first shot.

With a lack of federal guidance on low-risk activities Canadians can partake in after getting their first dose, experts are concerned about people filling in the blanks themselves and creating their own set of rules.

If someone does get infected after their first shot they could still end up in hospital, in the intensive care unit unable to be visited by their family, and potentially shipped off to a different hospital hundreds of kilometres away as the health-care system continues to be stretched beyond capacity.

But for now, that seems to be the exception. Infectious diseases specialist with University Health Network Dr. Isaac Bogoch says it's important Canadians know there is at least some layer of protection after your first shot.

"You're not afforded the same degree of protection as compared to having two doses of the vaccine. Having said that, it's still pretty significant protection, and depending on the data you read, you are protected from hospitalizaiton after a single dose anywhere from about 60 to 80 per cent," Bogoch said.

"People after a first dose should still take the necessary precautions. You still need to mask up, you still need to adhere to the public health measures, you still need to avoid crowded, confined spaces... we still have to do the right thing. It'll help, though. It really will help end this pandemic faster in Canada."

After the first dose and before the second dose of the Pfizer-BioNTech vaccine, the estimated efficacy is initially 52 per cent, but shoots to 92 per cent effective two to three weeks after the first shot.

Moderna's vaccine has an initial efficacy rate of 80 per cent after the first dose and increases to 92 per cent two weeks later.

The AstraZeneca shot is 76 per cent effective between 22 and 90 days after the first dose.

While these vaccines have exceptional data backing them, infectious diseases specialist with St. Joseph's Hospital in Hamilton, Dr. Zain Chagla, says no vaccine -- for anything -- is perfect.

"Anecdotally, the people that are in hospital after their first dose, where it's kicked in, are a lot less sicker than they could be. They're people that you expected to do worse," Chagla said.

Dr. Sumon Chakrabarti works at Trillium Health Partners in Mississauga, a hospital in one of Ontario’s hardest-hit areas. He says even though doctors there have seen the occasional patient who's gotten a first dose, and then let their guard down by say going to a social gathering, it is a small minority.

"We're just seeing so much COVID in Peel, where I am, that the chance of you getting COVID, regardless of vaccination status, is high, so there's many of those people that are getting infected just in every day life in the workplace, etc.," Chakrabarti says. "The vaccine is certainly doing something, (but) there is still a risk of getting hospitalized within a few weeks of vaccination."

Charkrabarti also focusses on the positive – since elderly and long-term care patients have been vaccinated for quite some time, he is seeing fewer and fewer of those patients in hospital.