The National Immunization Advisory Committee (NACI) recommends that provinces stop giving AstraZeneca in most cases — even as a booster dose to people who have already received their first doses of the product.
NACI said Thursday that AstraZeneca recipients should instead receive a second dose of the mRNA vaccine, such as those offered by Pfizer and Moderna.
“The mRNA vaccine is now preferred as a second dose for individuals who received the first dose of the AstraZeneca/COVISHIELD vaccine, based on emerging evidence of a better immune response than this combination vaccine schedule,” NACI said in a statement released today. “Mixed schedule vaccination” refers to the practice of using different products for the first and second doses.
The guidelines for shifting AstraZeneca doses from the supply chain come weeks after the NACI, an independent body of volunteer experts, said the AstraZeneca vaccine is not the “preferred” product for first doses due to risks associated with vaccine-induced immune thrombocytopenia (VITT) – a condition that causes blood clots Associated with a low platelet count.
The NACI said there is also a risk of developing a VITT after receiving a second dose of AstraZeneca. The rate of VITT after second doses of AstraZeneca is thought to be lower than the rate for first doses, but the NACI said the likelihood of developing this condition after getting a booster dose “has increased over time, with current estimates of about 1 per 600,000 people vaccinated.”
While the NACI initially said Canadians could opt for a viral vector vaccine such as AstraZeneca if they didn’t want to wait for an mRNA vaccine, the panel said today that guidance has “evolved” since then and a Pfizer or Moderna dose should be offered to “start a vaccine series, unless there is Contraindications, for example allergy to one of the components of the mRNA vaccine.”
The NACI said provinces could easily switch to an mRNA-based immunization campaign as Canada prepares to receive a deluge of shots from Pfizer and Moderna in the coming weeks, with an additional 14 million doses arriving this month.
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Since early May, all counties have stopped using AstraZeneca for first doses. Many continued to use it for booster shots.
The NACI said that people who have already taken two doses of AstraZeneca “can rest assured that the vaccine provides good protection against infection and very good protection against severe illness and hospitalization.”
Canadians who have already received a dose of AstraZeneca should know that NACI does not put the shot on a “blacklist” – they simply strongly prefer more readily available effective alternatives, said Dr. Donald Finne, an assistant professor of medicine at McGill University and an expert in microbiology and human genetics. .
“It’s not like there’s a recall of this product because it’s dangerous. There is nothing inherently wrong with the vaccine. It’s nothing evil. We’re just prioritizing vaccines that are best suited to current variants,” he said.
Evidence emerging from studies in Germany suggests that mixing one dose of AstraZeneca with a second dose of Pfizer’s vaccine can actually produce “a better immune response, including against variants of concern” than two doses of AstraZeneca alone, the NACI said.
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“Evidence continues to suggest that a first dose of AstraZeneca vaccine followed by a second dose of Pfizer-BioNTech mRNA vaccine has good safety,” NACI said.
A single dose of the AstraZeneca or Pfizer vaccine has been found to generate a significant antibody response to the novel coronavirus.
But a recent study by the UK’s Coronavirus Immunology Consortium and the University of Birmingham found that the AstraZeneca vaccine may actually be Stimulating a stronger cellular immune response From a Pfizer snapshot.
Based on early data, the mix-and-match system “performed very well and appeared to be highly responsive” as it produces both strong antibodies and a cellular response, said Dr Theresa Tam, Canada’s chief public health officer.
NACI now also recommends that mRNA recipients receive a second shot of whatever product they received first.
The NACI said the second shot should match the first unless “the product itself is not readily available, or the product used for the first dose is unknown. The two mRNA products can be considered interchangeable,” the panel said.
Brigadier General. Christa Brody, the military commander in charge of vaccine logistics, said Canada will receive about 9.5 million doses of Moderna by the end of the month — nearly 1.5 million more than the government expected.
That figure of 9.5 million includes the million doses that the United States donated to Canada this morning.
“That’s the big lift,” Brody said. “The vaccine supply is increasing rapidly.”
While Moderna’s offering is stabilizing after months of uncertainty and cut deliveries, Pfizer has made some adjustments to its July shipping schedule.
Prodi said Pfizer still plans to meet its commitment to send nine million doses to Canada next month, but the government now expects “less allocation in early July and more allocation later in July to make up for that.”