Astrazeneca to be held for 2nd doses

Alberta's remaining supply of Astrazeneca COVID-19 vaccine will be used for second doses only as supplies are running thin, the province's top doctor said Tuesday.

Chief medical officer of health Dr. Deena Hinshaw said at a news conference the province doesn't know when Canada and Alberta will get another shipment of this vaccine. The remaining supply of around 8,400 doses will be held for those who already had one shot — more than 255,000 people — and for those who can't get another type for medical reasons.

“We are holding our remaining Astrazeneca supply for either those who have a contraindication to an MRNA vaccine, or for second doses, recognizing that some Albertans will need a second dose beginning in early June,” she said at a news conference.

“This means that all new first dose appointments, unless there was a contraindication, are being booked with the MRNA vaccines Pfizer and Moderna.”

Alberta started doling out Astrazeneca in March — at first to those aged 50 to 64 before revising eligibility to 55 and older, then lowering it to 40 in April, and finally to 30 last week.

The recommended interval between doses is 28 days, and under that timeline many Albertans will soon be eligible for the second dose if they aren't already.

But Hinshaw said that Albertans will have to wait at least 12 weeks before beginning second doses for this vaccine because clinical trials show shortening the interval between shots offered less protection.

Alberta and the other provinces have been stretching intervals for all of the vaccines to up to 16 weeks in line with a recommendation from the National Advisory Committee on Immunization (NACI).

Hinshaw said last week that it is “very likely” that interval will eventually be decreased if supply allows.

Previously, the Canadian government purchased almost 24 million Astrazeneca doses of the vaccine and most are expected to arrive by the end of September.

Alberta hasn't decided whether individuals who had one dose of Astrazeneca vaccine can get a Moderna or Pfizer vaccine for their second shot, Hinshaw said.

She said the province is keeping an eye on the research, particularly the outcome of clinical trials in the U.K., where a major study is underway on the safety and efficiency of mixing doses.

Premier Jason Kenney said at a Tuesday new conference he doesn't regret not reserving supply of Astrazeneca vaccines for second doses, but doing so now is the right move.

“I think we made the right decision strategically, to go long on first doses to get broader population coverage,” he said.

Quebec will offer Moderna or Pfizer for second shots, and Ontario — which has stopped offering Astrazeneca as a first dose — may as well, pending results of the U.K. trial.

Canada's top doctor, Dr. Theresa Tam, is also watching that study.