The head of Ontario’s vaccine distribution task force wants Health Canada to look into allowing Moderna’s vaccine to be administered as one, less effective dose instead of two, allowing his team to ramp up their vaccination schedule across the province.
“We can’t vaccinate people any faster than we can if we don’t have the vaccines to do it,” Hillier said, speaking during a Tuesday press conference.
“I’m not asking Health Canada to change the Moderna from a two-shot vaccine to a one-shot vaccine. What I’m asking is Health Canada have a look at doing that, and saying maybe with the high efficiency that protects you in the first needle, it would be best for the entire population if we went just with a one-shot vaccination program with Moderna. I asked them to have a look at that.”
While provinces are sprinting to get needles into arms as quickly as possible, there is only so much that can be done as Canada awaits the arrival of vaccines.
Ontario came under fire for its initially slow rollout of its first vaccine shipments, but as they prepare to ramp up their vaccination schedule, Hillier says it would be worth studying whether the Moderna vaccine would be effective enough as a single dose.
There are currently two coronavirus vaccines approved for use in Canada, one of which is the Moderna vaccine. The vaccine currently requires two doses administered 28 days apart, with the initial dose providing 80 per cent protection before the second shot jolts that figure up to 95 per cent.
But one thing we don’t know is how long that initial 80 per cent effectiveness would last without a second dose.
The Pfizer-BioNTech vaccine, the only other COVID-19 vaccine currently approved for use by Health Canada, also involves two doses, taken some three weeks apart.
Both vaccines require two doses to hit around 95 per cent protection.
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And because the two dose-regimen is how both vaccines were studied and approved, this is how they must be administered, according to Dr. Zain Chagla.
“We give medications based on a monograph we give them based on how they’re dosed and how they’re studied in clinical trials,” he said.
“And so it’s very hard to then just invent a regimen, in that sense, and hope that it works based on subgroup analysis in a study or how the protocol wasn’t followed in the study.”
Moderna has only received regulatory approval in its two-dose form, meaning Hillier’s dream of a single-shot vaccine would require Moderna to submit new documents indicating the safety and efficacy of a one-dose version — a process that Moderna itself would have to be interested in undertaking.
And that’s also not a given, Chagla said.
“Taking the side of the company, they want their drug to work as best as possible,” he said.
“So I don’t think they’re particularly incentivized to also submit a regimen to Health Canada to say, well, this might work, it might be inferior – only to have their drug not work as well because they didn’t follow the optimal dosing strategy.”
Global News has reached out to Moderna for comment, but did not receive a response by the time this article was published.
Chagla also cautioned that even if Moderna wanted to submit that data, it might not actually exist. That’s because the vast majority of the vaccine recipients in the clinical trials were given two doses, not one.
“That data probably doesn’t exist significantly because, again, most of the people in the Moderna trial got both shots,” Chagla explained.
“And so there is a small subset that missed their (second) appointment…that’s probably not enough to leverage a decision that’s going to be mass vaccination campaign for the population.”
Health Canada’s chief medical adviser echoed Chagla’s comments during a press conference on Dec. 23.
“In terms of the clinical trials for the Moderna vaccine and for the Pfizer vaccine as well, they were both based on a two-dose regimen,” Dr. Supriya Sharma said.
She said that there are measurements of immunity before the second dose that, in the case of Moderna, are “quite high” — but the second dose was still eventually administered, leaving no answer as to whether that immunity drops off and how quickly that might happen.
“The question is how long does that immunity (last) and would it be lasting for that, you know, a significant period of time. So we would recommend that the second dose be given,” Sharma said.
She added that, for the Moderna and Pfizer vaccines, there can be “flexibility” in terms of when the second dose needs to be administered — but there isn’t enough evidence to say just how flexible that timeline might be.
“We haven’t seen anything in the evidence that would show that there would be a significant decrease in immunity if that is delayed for a few weeks. But again, we really don’t have the data to be able to say that, to confirm that one way or the other,” Sharma said.
Chagla said this could be an area where it would be worth investigating further. If it’s discovered that a longer delay between doses doesn’t impact the vaccine’s efficacy, it could help with the vaccine rollout logistics.
“Can we wait two weeks, four weeks and go off the monograph in that sense? Logistically, that might be a whole lot easier — to do people at eight weeks rather than four weeks,” he said.
For the time being, however, the vaccine must be administered as directed.
“The expectation is people get their second dose and…we give them their second dose,” Chagla said.
“We don’t stop doing it just because we want to save supply. We try to get the optimal immunity for the population.”
© 2020 Global News, a division of Corus Entertainment Inc.
