Canada Covid Update: thinking out loud

post by MalcolmOcean (malcolmocean) · 2021-03-22T21:39:43.550Z · LW · GW · 6 comments

Contents

  Vaccines
  New Strains - "Variants of Concern"
  Inconsistencies
  Officially hailing the control system
None
6 comments

(This started as a comment on Zvi's weekly post from 3/18 [LW · GW], but it got long and I started a second comment and I figured I might as well just make a new top-level post.)

I don't intend these posts to be consistent or exhaustive in the way that Zvi's are. They're mostly me thinking out loud as I try to figure out what's going on.

Here's a colorful overview from https://art-bd.shinyapps.io/covid19canada/ which I think is a day or two out of date:

Vaccines

Canada has now vaccinated over 10 doses per 100 people, and since we're now officially doing first doses first in most cases, that's nearly 10% of the population vaccinated. The territories, which have almost nobody in them, are like half-vaccinated already. Not sure what the thinking was there (sometimes northern regions have it really rough?) but in any case it's nearly a rounding error on the doses needed for provincial populations, so seems reasonable to just get it over with.

We have 38M people, 940k cumulative confirmed cases, 4M vaccine doses administered.

Interestingly, while we're way behind the USA on administering vaccine doses (they're at 37 doses per 100 people), we've already soared way past the "more people vaccinated than ever tested positive" figure because we had fewer people test positive in the first place. From a timeline perspective though, that unfortunately means we're even further from herd immunity than being so behind on vaccines would imply.

Vaccine timelines are speeding up here a bit though and it's looking like with first doses first and a few bonuses we might actually have a shot in everyone's arm by July. (Everyone ofc means everyone over the age of 16 (31.5M) who wants to (about 79% of that, according to a poll I found somewhere))

From CBC

I don't know if that's just an arbitrary date they're intending to allow large Canada Day celebrations on July 1st if indeed this is achieved. It think it would be really meaningful to do that, though might be unwise given that many of those adults would have been vaccinated on like June 29th or 30th so could still get sick if they caught the virus in the following few days.

New Strains - "Variants of Concern"

Searching for data about the new strains (eg B.1.1.7) in Canada... aha, I found this official statement from March 16th. Which links to even better data. Okay, if we assume that the proper denominator here is the total number of confirmed cases over the past couple weeks/months (about 400k) then this is a small (but growing) fraction.

To do some really simple math, if there were 4086 VOC cases as of March 16th (from statement above), and 5154 VOC cases March 21st (adding up the top row of the table above)......... that is not good?

Without even considering the overall case #s, that's 5% day-over-day growth, which is a 2-week doubling time, which suggests... 10k VOC cases by Apr 4, 20k VOC cases by Apr 18, 40k VOC cases by May 2, 80k VOC cases by May 16, 160k VOC cases by May 30, 320k cases by June 14, 640k VOC cases by June 28...

Okay, that's bad but it's only the same order of magnitude of how bad things were the last couple months anyway, not higher. And in principle things should seriously be slowing by that point as front-line workers get vaccinated and the weather improves.

Now looking at overall case numbers, there were 18k total cases reported in that same 5-day window. Although wait.... oh, oh no. The 4k→5k VOC increase might be naive since some of those 4k cases would have resolved months ago. So the number of active VOC cases would have increased a lot more in the last week. So maybe it's more like a 10% day-over-day growth, which would be about a 1-week doubling time, which is a lot worse. Somehow that seems unlikely, since say conservatively we imported a dozen VOC cases from other countries last December, and none since, 1 doubling per week would put us at 25000 VOC cases by now. 2-week doubling time seems about right actually.

I am not confident in my math or reasoning here, but I'm enjoying thinking out loud. Feel free to point out any issues you spot!

As Zvi noted, things might also be particularly worse in some regions in Canada, eg Regina seems to have it bad with new strains.

Inconsistencies

Hang on. This all seems inconsistent with this other report from a few weeks ago:

COVID-19 variants likely to make up 40 per cent of Ontario cases by mid-March, hospitalizations expected to climb

In this CTV News article...

“It’s the presence of cases caused by new variants that’s alarming,” Dr. Peter Juni, scientific director of the Ontario COVID-19 Science Advisory Table, told CTV’s Your Morning on Wednesday.

He said that in Ontario, variant cases have already exceeded 50 per cent of all cases.

It can't be the case that:

• there are <1400 variant cases total in Ontario
• this is >50% of all cases
• there are >10k active cases in Ontario at the moment and >1000 new cases each day

Those numbers don't add up. I don't know what's going on 

Officially hailing the control system

This isn't exactly news but I just discovered that Ontario actually publishes a graph of its estimated effective R number, over time, and sure enough, it tracks right around 1. I'm pretty angry personally at Ontario/Canada easing up restrictions so much last summer when cases were almost at zero, allowing them to grow right back up into the fall. We could have been Australia by this point, with zero cases.

(Zvi posits a distributed control system that when R goes below 1, people & policies get more lax to bring it back to 1, and when it goes above, things tighten to bring it back to 1. This is not wise! Marginal Revolution has a great post on this: The non-linearity of Covid-19 response)

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