Administering most of Canada’s coronavirus vaccines now, as opposed to reserving half of them to be used later as second doses for the first recipients, could prevent a significant amount of new symptomatic COVID-19 infections, according to new data from researchers at the University of Toronto.
The results of the modelling, which were first reported by The Globe and Mail, come amid plans from provinces such as Ontario to keep half of their initial shipments of the COVID-19 vaccine in case future deliveries of the vaccine are delayed.
Ashleigh Tuite, an epidemiologist at the University of Toronto’s Dalla Lana School of Public Health, presented her findings to Ontario’s COVID-19 Science Advisory Table on Tuesday.
Based on her team’s study, Tuite told Global News that withholding fewer doses during early distribution of the vaccine — so that more people can be immunized as soon as possible — could prevent an additional 25 to 40 per cent of symptomatic COVID-19 infections, compared to a more conservative approach that would reserve half of each vaccine instalment for the second dose.
The cost of the more conservative approach would be “to delay receipt of first doses in many people who could gain substantial health benefits from earlier vaccination,” according to the paper, which is still under review.
Tuite’s and the other researchers’ findings also comes just a day after Health Canada approved Moderna’s COVID-19 shot, now the second available vaccine the country can use to immunize against the virus.
Moderna’s vaccine approval now puts pressure on whether provincial governments should hold back half of their vaccine shots due to it being easier to store and administer in nursing homes and rural areas.
That’s because of its less stringent transport requirements than the Pfizer-BioNTech vaccine, a shot that has to be transported at -70 C.
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In order for both vaccines to reach their maximum efficacy, two shots have to be administered over a period of several weeks. Pfizer’s second dose would have to be administered 21 days after the first shot, while Moderna’s would come after 28 days.
According to infectious disease expert and epidemiologist Dr. David Fisman, Canada should be vaccinating with as much of the doses it has on hand as fast as possible.
“The basic idea is that we actually have more and more and more vaccine coming week on week on week, so it makes no sense right now — given the number of people who are dying and given how effective this vaccine is — that we would set vaccine aside for three weeks from now, because that’s going to result in a lot more people dying because they haven’t been vaccinated at all,” Fisman told Global News.
“And in fact, you see a lot of protection right around the time that that second dose is given, which tells us that that’s not from the second dose, right, because it takes time for an immune response to develop.”
Fisman said that we should still want to give people that second dose, but that we should administering as much of the vaccines as possible given the urgency of the pandemic.
A statement from Ontario said that no formal recommendations to administer more of its doses as opposed to saving them have yet been made.
It also confirmed that they would continue giving second doses to patients after they were administered their first. Saskatchewan, B.C. and New Brunswick have all said they don’t plan to hold back doses.
Dr. Peter Jüni, the scientific director of the science advisory table, says that it “seems to be safe” to invest into vaccinating as many people as we can with the doses we have now. According to Jüni, two of the presentations came to the conclusion that frontloading the doses and not reserving them in installments as second doses would be a more “efficient” strategy in tackling the spread of COVID-19.
Newly-released recommendations from Canada’s National Advisory on Immunization (NACI) presented several ethical considerations on whether or not vaccines should be held back for a second dose or used on as many people as possible, with the committee’s report identifying factors like having an informed choice and minimizing the risk of harm versus the benefits of holding back or administering all their vaccines.
Canada’s first shipments of the Moderna vaccine, which arrived Thursday, is set to be widely distributed to Canada’s nursing homes — which house seniors at highest risk of a severe outcome from being infected — as well as to the territories.
The country is set to receive 168,000 doses by the end of December.
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