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'Legitimate' questions raised about further delaying second vaccine doses: Ottawa

Officials also confirm weekly Pfizer shipments for final stretch of March
New data shows the first dose of the coronavirus vaccine is highly protective, meaning delaying or doing away with a second dose isn't off the table.

Further delaying a second COVID-19 vaccine dose — or even shifting Canadians from two doses to one — isn’t off the table, according to one of the country’s top doctors.

Dr. Howard Njoo, Canada’s deputy chief public health officer, said Thursday “legitimate” questions about such a plan are being raised by a pair of Canadian doctors in correspondence submitted to the New England Journal of Medicine.

“With such a highly protective first dose, the benefits derived from a scarce supply of vaccine could be maximized by deferring second doses until all priority group members are offered at least one dose,” Dr. Danuta M. Skowronski of the B.C. Centre for Disease Control and Dr. Gaston De Serres of the Institute National de Sante Publique du Quebec wrote in a piece published this week.

“There may be uncertainty about the duration of protection with a single dose, but the administration of a second dose within one month after the first, as recommended, provides little added benefit in the short term, while high-risk persons who could have received a first dose with that vaccine supply are left completely unprotected.”

Njoo confirmed during a virtual press conference that federal officials have been briefed on the potential of only providing one dose of the Pfizer Inc. or Moderna Inc. vaccines.

He said officials must weigh the balance between protecting a larger number of people with one dose vs. smaller number with two doses.

Both the Moderna and Pfizer vaccines require two doses for maximum efficacy.

“Those deliberations and discussions are very live and ongoing right now,” Njoo said a day after the piece was published.

Both vaccine manufacturers recommend intervals of about three to four weeks between doses.

B.C. has stretched that interval over the past few weeks, first from 35 days and then to 42 days.

Provincial health officer Dr. Bonnie Henry said on Tuesday that 4,000-6,000 British Columbians are likely to receive their second Moderna dose more than 42 days after their initial dose.

This comes amid shipping delays from Moderna.

Henry spent an extended period during a Tuesday media briefing attempting to allay concerns about that interval between doses, citing research from the U.K. and Israel indicating that delays of second doses do not have a negative impact on vaccine effectiveness.

She also noted some jurisdictions are stretching the interval to as many as 90 days.

Meanwhile, Maj.-Gen. Dany Fortin, the vice-president of logistics and operations at the Public Health Agency of Canada (PHAC), confirmed at the same briefing that Canada would be receiving 444,000 Pfizer doses all five weeks of March.

Last week, the federal government was only able to confirm 444,000 doses would be arriving the first two weeks of March ahead of the manufacturer’s push to meet its obligation of delivering four million doses by the end of next month.

With the confirmed shipments for the final weeks of March, Pfizer is set to meet its obligations following weeks of shipping delays brought on by the company’s efforts to revamp its facilities in Belgium to expand manufacturing capacity.

Moderna is expected to deliver 1.2 million over two shipments before the end of next month, according to Fortin.

The exact number of doses in each of those two shipments has not yet been confirmed.

In addition to the combined six million doses Pfizer and Moderna are set to deliver by the end of March, the two manufacturers are also contracted to deliver 23 million additional doses between May and June.