Alberta considers further extending time between doses of COVID-19 vaccine

Alberta is considering delaying the timing of second doses of COVID-19 vaccines even more, one day after B.C. announced it is extending the time between doses to 112 days.

Currently, the second dose of vaccine is being delayed up to 42 days in Alberta – a decision that was made after issues with vaccine supply earlier this year. Vaccine manufacturers Pfizer and Moderna propose intervals of 21 and 28 days, respectively.

Health Minister Tyler Shandro said on March 2 that the province is considering following in B.C.’s footsteps.

Shandro said they are looking at evidence coming out of other jurisdictions as well as reviewing advice from physicians and the province’s vaccine advisory committee but he signalled a change will be coming.

“What the exact period of time it’s going to be is still to be decided. We will be announcing it soon. We will be looking at having that length of time between first and second [doses] extended,” - Tyler Shandro

Chief medical officer of health Dr. Deena Hinshaw said on March 2 that decisions are being based on the available evidence, which is constantly evolving with COVID-19.

“One of the things that’s really encouraging that’s coming out of real-world experiences with using the Pfizer and Moderna vaccines, is seeing high levels of protection from the first dose that last for several months,” Hinshaw said.

There is no word on when a decision will be made. The National Advisory Committee on Immunizations is looking at the evidence to support the time span between the doses and is expected to release its findings later this week. The deliberations over whether to delay a second dose even further comes as epidemiologists call on Canada to get more first doses into arms.

“In the short term, you can potentially vaccinate twice as many people knowing that you do have (time) to give them their second doses in the future,” said Ashleigh Tuite, an infectious disease epidemiologist at the University of Toronto. This could “potentially save more lives and prevent more hospitalizations and more severe outcomes,” she said.

However, Dr. Mona Nemer, Canada’s chief science advisor, said not all viruses act the same way and therefore, not all vaccines act the same way.

“I’ve said it before, this is the first time that we have RNA vaccines. We don’t know how our bodies respond to them. We don’t know how strong immunity is and how long it lasts.”

“So I think we need to maintain some humility in the face of this evolving science and to maintain public trust, that we be open and transparent about the data that is being used for decision-making,” Nemer added.

Preliminary data from Quebec shows its strategy of spacing doses a maximum of 90 days apart is paying off. The National Institute of Public Health of Quebec (INSPQ) said on Feb. 18 that both vaccines from Pfizer-BioNTech and Moderna are said to be approximately 80 per cent effective in preventing disease 14 to 28 days after the administration of a first dose.

There is also emerging early evidence in support of protection and reduced transmission after the first dose.

A new study on Friday by Cambridge University in the U.K. suggests that a single dose of the Pfizer-BioNTech vaccine can reduce fourfold the number of asymptomatic COVID-19 infections. The results of the study are yet to be peer-reviewed.

Another Israeli study published in the Lancet medical journal last week found an 85 per cent reduction in symptomatic COVID-19 infections within 15 to 28 days of receiving a first dose of the Pfizer vaccine.

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