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Vaccine update: Some Moderna, AstraZeneca recipients face extra hurdles for second doses

NACI unveiled new recommendations earlier in the week on vaccine interchangeability
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The National Advisory Committee on Immunization (NACI) released new guidance on Tuesday, giving the nod to mixing and matching doses of COVID-19 vaccines but only under very specific circumstances.

Some British Columbians who received the Moderna Inc. COVID-19 vaccine for their first dose may have to rebook their second-dose appointments this month as the province unveils plans for mixing and matching vaccines.

B.C. provincial health officer Dr. Bonnie Henry says Moderna recipients will have the option of either accepting the Pfizer Inc. vaccine for their second dose or else waiting until more supplies of Moderna become available.

“You can choose to rebook in June when more Moderna is available but I would encourage everyone to take the vaccine that you are offered when you go in for your second dose,” she said during a Thursday briefing.

“You can be assured that we have looked at this evidence with millions of people. It is safe and effective.”

The National Advisory Committee on Immunization (NACI) released new guidance on Tuesday, giving the nod to mixing and matching doses of COVID-19 vaccines but only under very specific circumstances.

Henry said that it is safe and effective to get a different vaccine “if you need to.”

“It’s equally safe and works just as well to have either mRNA vaccine,” she said.

Health officials at both federal and provincial levels have said it’s preferable Canadians are inoculated with the same product for both doses but the new recommendations now offer flexibility.

Canada is facing supply issues with AstraZeneca, which is a viral vector vaccine, while mRNA vaccines like Pfizer and Moderna have made up a far more significant portion of the country’s supply.

Canadians who received AstraZeneca for their first shot may receive AstraZeneca for their second shot or else an mRNA vaccine for their second shot, according to NACI’s recommendations.

"This is not a new concept. Similar vaccines from different manufacturers are used when vaccine supply or public health programs change. Different vaccine products have been used to complete a vaccine series for influenza, hepatitis A, and others," the committee said.

But it’s not a two-way street.

“Persons who received a first dose of an mRNA vaccine (Pfizer-BioNTech or Moderna) should be offered the same mRNA vaccine for their second dose,” according to the recommendations.

NACI said if the same mRNA vaccine is not readily available, another mRNA vaccine can be considered interchangeable.

Henry said the possibility of mRNA mixing and matching will mostly affect those who received the Moderna vaccine for their first dose, owing to “spotty” supply issues, but it will ultimately be up to British Columbians to decide if they use different vaccines.

Meanwhile, B.C.’s top doctor said the province would begin shipping out second doses of the AstraZeneca plc vaccine on Thursday in a bid to begin administering the jabs by Monday.

AstraZeneca was being administered in B.C. at pharmacies and pop-up clinics rather than at the mass vaccination sites where Pfizer and Moderna have been administered.

Henry also repeatedly urged British Columbians not to call pharmacies to book an appointment, adding that pharmacies will reach out proactively.

“They will not be accepting appointments if you call them,” she said.

Henry said about 20,000 doses of AstraZeneca are due to expire June 27 and June 30 after officials were able to extend the expiration dates for those specific lots.

“We are quite confident that starting next week, when people are due for second doses, there’s enough that we’ll be using that up first. The rest of the 150,000 doses that we have on hand don’t expire until later in the summer, so that’s not an issue for us,” she said.

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