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A dose of the Pfizer-BioNTech COVID-19 vaccine is prepared by Pharmacy Technician Supervisor Tamara Booth Rumsey at The Michener Institute in Toronto on Jan. 4, 2021.Frank Gunn/The Canadian Press

Health Canada has approved a label change to Pfizer-BioNTech’s COVID-19 vaccine that will see an extra dose withdrawn from each vial, giving the Liberal government’s beleaguered vaccination campaign a boost but putting more pressure on the people administering the shots.

Officials with the federal regulator said Tuesday that six doses, rather than five, can be “obtained reliably and consistently” from each vial of the vaccine. That rebuts the position from some provincial officials, who have said the sixth dose should be treated as a bonus because the extra shot cannot be reliably extracted.

Health Canada’s senior medical adviser, Supriya Sharma, said Pfizer has shown that with the right training and equipment, medical professionals will be able to extract six doses from each vial of the vaccine, without the manufacturer having to change the amount it puts in each vial.

“The company did the assessment with about nine different combinations of syringes and needles, and in all cases they were able to extract that sixth dose,” Dr. Sharma said.

To successfully do so medical professionals need to use specialized low dead space syringes for each dose. The syringe limits the space between the needle and the plunger when it’s fully pushed in, meaning only a maximum of 0.035 millilitres of vaccine is wasted per shot. The syringes are in short supply around the world, but last week Procurement Minister Anita Anand said the federal government has purchased 64 million low dead space syringes, all of which will be delivered by May.

Pfizer asked Health Canada to make the label change after regulators in the United States and European Union had already done so.

Major-General Dany Fortin, who is leading Canada’s vaccine logistics, said Tuesday the federal government believes the provinces were not using the low dead space syringes when they said they couldn’t reliably extract six doses per vial. He said the Public Health Agency of Canada will start counting the sixth shot with next week’s shipment. The change is being made in concert with the distribution of the first shipment of the specialized syringes to the provinces.

Pfizer’s contract with the federal government is based on the number of doses, so the company will be able to send fewer vials to Canada while still meeting its commitment to ship four million doses by the end of March and a total of 40 million shots by the end of 2021. The Health Canada decision won’t change how many vials Pfizer ships in February. So next week Canada will count 403,650 doses in its shipment, up from 336,375 shots.

While the change leaves less room for error, Marc Berthiaume, the director of Health Canada’s Medical Science Bureau, said there is still a sufficient buffer. The regulator said that after six 0.3-millilitre doses have been administered, at least 0.24 ml of vaccine remains in the vial.

That buffer can be increased if staff more efficiently extract their shots, meaning a seventh dose can sometimes be squeezed from a vial, Dr. Sharma said.

For example, the Niagara Region Public Health Unit reports it’s been so efficient in its vaccination campaign that almost 28 per cent more people were able to get their shots and it’s able to draw seven doses 50 per cent of the time.

Manitoba has already been counting six doses per vial, but Ontario, Alberta and Saskatchewan have argued it’s not always possible.

Alberta has previously complained that counting each Pfizer vial as six doses would shortchange the province because the government’s own analysis estimated staff could only get that extra dose 75 per cent of the time. On Tuesday, Deena Hinshaw, Alberta’s Chief Medical Officer of Health, said the province has secured enough of the low dead space syringes that she’s confident health care workers will be able to consistently get the extra dose.

“There’s always some potential wastage, but I would imagine it would be much closer to 100 per cent based on the trials that Health Canada has reported to us,” she said at a briefing on Tuesday.

The federal government did not say whether Pfizer will send supplemental doses if only five are extracted from a vial.

With a report from James Keller

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