By delaying the second dose of the COVID-19 vaccines, Canada may be able to meet vaccination targets ahead by several weeks.
If the spacing between doses “were to be increased” based on the anticipated delivery of vaccines in Canada, “the timelines would shift,” Dr. Howard Njoo, Canada’s deputy chief public health officer said during a press conference Thursday.
It could fast-track vaccinations for the “vast majority of the Canadian population in an advanced timeline, or move it up by several weeks,” he said.
This comes following Canada’s National Advisory Committee on Immunization (NACI) recommendations Wednesday that provinces and territories could extend the interval between first and second COVID-19 vaccine doses up to four months.
“Extending the dose interval to four months allows NACI to create opportunities for protection of the entire adult population within a short timeframe,” the committee said.
Njoo echoed the committee’s suggestions and said, “NACI bases data on evolving evidence in a real world context.”
Several provinces across Canada have already given nod to the NACI advisory in order to fast-track the vaccination process.
In a cabinet meeting Thursday, Nova Scotia Premier Iain Rankin said everyone in the province could get their first shot of the COVID-19 vaccine by the end of June.
“Logic would follow that we wouldn’t have to hold back the second dose,” he said.
British Columbia too, is expecting all adults in the province to have the option to receive their first dose before the end of July.
Provincial health officer Dr. Bonnie Henry announced Monday that the gap between the first and second doses of the vaccine will be extended to 112 days.
Efficacy studies of the vaccine have shown that receiving a first shot of the vaccine is over 90 per cent effective for at least a few months, Henry said.
“That is why I am so confident that the decision we made, over this weekend, to extend that interval is the best one based on all of the science and the data that we have to maximize the benefit to everybody in our community here in B.C.,” Henry added.
Following this, Newfoundland and Labrador announced Wednesday the province was extending the interval between the first and second doses of the COVID-19 vaccine to four months.
Provincial health officials said the change will help them vaccinate 40,000 more people with a single dose by the end of March.
Saskatchewan Premier Scott Moe said Thursday that the prairie province would also follow suit and extend the gap between doses. Other provinces, such as Alberta and Ontario, have signalled they plan to do the same.
A recent study published by the New England Journal of Medicine has found that Pfizer’s COVID-19 vaccine is 92 per cent effective at preventing severe disease after two shots and 62 per cent after one.
The AstraZeneca vaccine too is being said to be more effective when its second dose is given three months after the first, instead of six weeks, a peer-reviewed study published in The Lancet medical journal says.
Efficacy was found to be at 81 per cent with the longer interval of 12 weeks between the first and second dose, compared with 55 per cent efficacy up to the six-week gap, according to the Lancet study.
Based on data available so far, there is “reasonable assurance” that it’s fine to extend the window between the doses, Dr. Ronald St-John, former director general of the Centre for Emergency Preparedness and Response at PHAC told Global News.
“We know that there’s such a good response to an immune system after three to four weeks that extending the time to the next booster dose is reasonable,” he said.
“We now know more about the immunity from natural infection and that we get immune response up to six months and probably longer from natural infection. So the first dose is kind of mimicking the natural infection,” he added.
More than 2 million COVID-19 vaccine doses have been administered to Canadians to date, of which 3.6 per cent have received one dose and 1.4 per cent have got two shots.
—With files from Mike Le Couteur and Global News