Ottawa approves six-week gap between doses as it waits on vaccine shipments,
Officials say it’s safe to space out initial, booster shots by up to 42 days
OTTAWA—The federal government has changed its COVID-19 vaccine recommendations, telling provinces they may delay administering a second injection by up to three weeks while the country awaits a sharp increase in supplies that’s expected in April.
That’s when Maj.-Gen. Dany Fortin said Canada will receive on average more than 1 million doses a week of the Pfizer/ BioNTech and Moderna vaccines.
A total of 20 million doses is expected to arrive between April and June. That number could increase more rapidly if either of two other vaccines being studied by regulators is approved.
Dr. Howard Njoo, deputy chief public health officer of Canada, said the National Advisory Committee on Immunization and the World Health Organization now agree that it is possible to safely space out the initial and booster shots of the Pfizer/BioNTech and Moderna vaccines by up to 42 days, instead of the manufacturers’ recommended intervals of 21 and 28 days respectively.
But there is not enough data, Njoo said, to show how long immunity lasts beyond 42 days, so he urged provinces to stick to the recommended dosing intervals of the two shots.
Njoo said there is a “strong consensus” among all chief medical officers of health in Canada that “only in exceptional circumstances” should provinces plan for a longer interval of up to 42 days. However, he refused to criticize Quebec for taking a different path, citing “realities on the ground.”
With COVID-19 infection rates growing, Quebec announced it will delay a second dose for those now being vaccinated by up to 90 days, more than double the federal recommendation.
Njoo acknowledged there is a limited supply of vaccine for now, and in provinces like Quebec, there is an “ethical perspective” that decision-makers are weighing, “the fact there’s an increased rate of cases, hospitalizations, deaths. There’s more widespread transmission in certain parts of the country.”
Richard Massé, Quebec’s strategic health adviser, and Health Minister Christian Dubé denied Thursday that they were taking a risk in ignoring the companies’ recommended protocols.
Massé said the province was taking a “very informed” and “safe decision” to “immunize as many people that are very vulnerable to disease, hospitalization and death,” and would monitor how long immunity lasts in vaccine recipients who get just one dose.
“Immunity is not something that is on or off and that it stops after 42 days,” he said, citing experience with other two-dose vaccines and immunologists who he said agree with Quebec’s position.
Prof. Tania Watts, a professor of immunology at the University of Toronto’s faculty of medicine, said in an interview that the science behind immunization shows that boosting or giving a second shot “can be very important. It increases the size of an immune response but also importantly, how long the immune response lasts.”
The clinical trials for Pfizer/ BioNTech showed up to 95 per cent efficacy for the vaccine with two doses spaced the way the companies recommend, but the studies “have not gone on long enough to see how long the protection lasts,” she said.
“The really important thing is that you get the second dose, and that you get it before your immunity drops off too much, because what we’re really worried about, particularly with the virus running rampant, is the more you allow the virus to replicate in people, the more it can mutate. And if we have people that were not fully immunized getting infected, we worry about the virus maybe mutating to escape the immune system.”
Watts said the recommended intervals are “really just what they tested it at. It doesn’t mean that that’s a magical number, and it (the second dose) doesn’t work later.”
But Watts said a 42-day interval “is a fairly prudent relatively safe extension.”
“There’s every expectation that you’ll get a helpful benefit, but the caveat is that we’re breaking with the protocol that was approved by Health Canada. What would be very bad is not to give the second dose at all. We’d be in a very bad position if seven or eight months from now immunity has fallen off and people hadn’t gotten their second dose.”
A document explaining Quebec’s rationale said estimates of vaccine efficacy “between day 14 after the first dose and up until the second dose range from 69 per cent to 98 per cent, suggesting high protection (69 per cent) from a single dose during this observation period, even in the worst-case scenario.”
It said that in the case of other kinds of vaccines that require boosters, “the first dose by far provides the greatest share of the protection.”
Massé acknowledged “it’s possible that there would be a decrease” in the immune response in those patients who don’t receive a timely second dose, but said “we are monitoring that.”
“We know that delaying from 42 days to 90 days is a short period of time, and if there is anything that we see that indicates that certain people will have decreased immunity, we will give immediately the second dose.”
Quebec announced it will delay a second dose for those now being vaccinated by up to 90 days, more than double the federal recommendation