Saskatchewan expects to receive enough AstraZeneca-Oxford vaccine doses to give one to everyone who received it as a first shot.
On Wednesday, 20,400 doses of AstraZeneca arrived in Saskatchewan. The province's chief medical health officer Dr. Saqib Shahab said those awaiting a second dose should expect to receive it 12 weeks after their first shot.
"We will be prioritizing bookings for AstraZeneca patients so that they can get right in the week that they become eligible," Shahab said.
On Tuesday, the province's top health officials provided an update on vaccinations.
Shahab said those who received a first dose of AstraZeneca will be able to get the same brand for a second dose.
He said effectiveness of AstraZeneca is improved with more time between doses, up to 12 weeks.
"We've also learned that AstraZeneca from the U.K., other jurisdictions, that if you optimize the second dose at 12 weeks, you'll get the highest long-term protection with AstraZeneca."
Shahab said with AstraZeneca doses being administered in Saskatchewan in the middle of March, those who received it will start to become eligible in the first week of June.
"The second dose of that 12 weeks will be for most people starting in the first week of June and continuing till the end of June, early July."
Despite that advice, the government is still awaiting guidance on the use of the vaccine and timing.
"We are still waiting on advice on the use of AstraZeneca, including the timing of second doses," said Derek Miller, the Saskatchewan Health Authority's emergency operations centre lead.
The government diverted 15,500 doses of AstraZeneca to Regina in March and distributed them in the drive-thru to people in their 60s.
Shahab is among the more than 72,000 people who received AstraZeneca in Saskatchewan with their first dose. Last week, the province announced it was no longer giving the vaccine out as a first dose due to lack of supply.
The federal government has not provided an update on future shipments, after this week's shipment.
Saskatchewan's Minister of Health Paul Merriman said he was "very confident" in the flow of vaccines into the province in June.
He said the ideal timing of second doses differ because of what studies have shown to be the optimum intervals for protection.
He said those getting a second dose of Pfizer or Moderna in May and June may receive it eight weeks after their initial shot.
He said that interval could shrink in July to three weeks for Pfizer and four weeks for Moderna.
The government said in a news release Tuesday it planned to match first and second doses by brand.
"National reviews of the safety and efficacy of interchanging the second dose brand are ongoing and the provincial policy on maintaining the same brand for the second dose may be updated following this review."
Shahab said Tuesday that results of the latest study are expected by the end of May.
Some provinces pause AstraZeneca first-dose use
More than two million Canadians received a dose of AstraZeneca.
The country received 655,000 more doses of the vaccine this week.
Ontario, Quebec and Nova Scotia stopped using AstraZeneca last week for first doses, citing the small but potentially dangerous risk of vaccine-induced immune thrombotic thrombocytopenia (VITT), a blood-clotting condition that can cause fatal bleeding.
As of last week, there were 18 confirmed cases of VITT after vaccinations of AstraZeneca, including three deaths in Quebec, Alberta and New Brunswick, with 10 other possible cases under investigation.
In the United Kingdom, where the majority of people have been inoculated with AstraZeneca, there have been 242 reports of VITT and 49 deaths out of 28.5 million doses given.
Dr. David Naylor, co-chair of Canada's COVID-19 Immunity Task Force, said those who received the shot more than a month ago are outside of the risk for VITT.
He said early data from the United Kingdom also suggests the risk of VITT with the booster shot is an order of magnitude lower than with the first dose.
Last week, a Saskatchewan woman in her 60s was the first to have a confirmed case of VITT in the province. The government said she received treatment and is recovering. She received her dose on April 11.