Thread by @MoriartyLab

Here's are estimates of severe BREAKTHROUGH COVID-19 outcomes, by age group, in Canada or comparable OECD countries.

Remember, risk of these outcomes are 7-9X higher in UNVACCINATED people.

These are based on the age-specific OECD infection fatality rates for Alpha (so quite conservative), and assume that vaccine protection vs severe outcomes in double-vaxxed people has dropped from 90% to 70% for Omicron, as per recent South African reports.

They're estimates, but remember that Alpha was "milder" than Delta, and that monoclonal antibodies we use for treatment also look like they're taking a big hit with Omicron. These estimates may be revised up/down, but probably not by huge amounts. They're decent ballparks.

OK, let's walk through the calculations, using people in their 40s as an example. The OECD IFR for this age group, for Alpha, is ~0.1271%. That means that 1 in 788 unvaccinated people in their 40s died of COVID-19 if they contract it.

Now, let's vaccinate those people with two doses. This gives 90-95% protection against severe outcomes--more like 90% with Delta. The IFR for people in their 40s now drops to 0.1271% x 0.1. This means 1 of every 7,868 double-vaxxed people in their 40s die of COVID-19.

Ach. To clarify. I keep phrasing this in a short-hand way that is not clear. 1 of every 7,868 double-vaxxed people in their 40s who contract COVID-19 will die of it.

If protection against severe outcomes has dropped from 90% to 70% for Omicron, then for people in their 40s, the IFR drops to 0.1271% x 0.3. This means 1 of every 2,623 double-vaxxed people in their 40s who contract COVID-19 will die of it. Much better odds than for unvaxxed.

But you can see how having enormous numbers of infections will lead to a significant number of breakthrough deaths, even among people in their 40s.

I'll talk about that later in the thread, but first will provide hospitalization and ICU admission estimates.

FYI, the sources for the OECD infection fatality rates, hospitalization rates and ICU admission rates are found at the bottom of the page here: docs.google.com/spreadsheets/d…

OK, for people in their 40s, the ICU admission rate for unvaccinated people is 0.46%.

This means 1 of every 217 unvaxxed people 40-49 who contract C19 end up in ICU.

Estimate for double-vaxxed people, Omicron is 0.46% x 0.3 = 1 of 725 double-vaxxed people 40-49 w/ C19 in ICU.

Hospitalization rate for unvaccinated people in their 40s who contract COVID-19 is 2.1%. 1 of every 48 unvaxxed people 40-49 who contract C19 are hospitalized.

Double-vaxxed, Omicron: 2.1% x 0.3 = 1 of every 159 double-vaxxed people 40-49 w/ C19 hospitalized.

If you're in your 50s, the infection fatality rate for Alpha is 0.4254%. ICU admission rate is 1.2%. Hospitalization rate is 4.4%.

For unvaccinated people in their 50s who contract COVID-19, 1 in 235 die, 1 in 83 end up in ICU, 1 in 23 are hospitalized.

For double-vaxxed people in their 50s who contract COVID-19 (Omicron), estimate is that 1 in 784 will die, 1 in 278 will end up in ICU, 1 in 76 will be hospitalized.

I'll also do the calculations below assuming there is no loss of vaccine protection vs Omicron, just FYI.

If you're in your 60s, the infection fatality rate for Alpha is 1.4231%. ICU admission rate is 3.3%. Hospitalization rate is 8.9%.

For unvaccinated people in their 60s who contract COVID-19, 1 in 70 die, 1 in 30 end up in ICU, 1 in 11 are hospitalized.

For double-vaxxed people in their 60s who contract COVID-19 (Omicron), estimate is that 1 in 234 will die, 1 in 101 will end up in ICU, 1 in 38 will be hospitalized.

If you're in your 70s, the infection fatality rate for Alpha is 4.7611%. ICU admission rate is 6.85%. Hospitalization rate is 17.1%.

For unvaccinated people in their 70s who contract COVID-19, 1 in 21 die, 1 in 15 end up in ICU, 1 in 6 are hospitalized.

For double-vaxxed people in their 70s who contract COVID-19 (Omicron), estimate is that 1 in 70 will die, 1 in 49 will end up in ICU, 1 in 20 will be hospitalized.

If you're in your 80s, the infection fatality rate for Alpha is 18%. ICU admission rate is 2.19%. Hospitalization rate is 28.72%.

Remember, most people in their 80s won't survive ICU itself, independent of COVID, so they don't end up there. Lots more people with DNRs too.

For unvaccinated people in their 80s who contract COVID-19, 1 in 6 die, 1 in 46 end up in ICU, 1 in 4 are hospitalized.

Double-vaxxed people in their 80s who contract COVID-19 (Omicron): about 1 in 19 will die, 1 in 152 will end up in ICU, 1 in 12 will be hospitalized.

OK. Now let's do this assuming that Omicron is the same severity as Alpha (less severe than Delta), and vaccines continue to provide 90% protection against severe disease with this variant.

The odds for unvaccinated people remain same, of course, because they have no protection.

I'd also like to pause to note that Canada's infection fatality, ICU admission and hospitalization rates are actually generally higher than the OECD values I use for calculations, likely because we under-detect mild/asymptomatic cases.

So, if you're double-vaxxed and there's no reduction in protection from severe illness for the vaccines from Omicron, or perhaps if you're triple vaxxed and are back up to normal vax protection levels (90%), here is what you'd expect.

Basically it's the infection fatality, ICU admission and hospitalization rates multiplied by 0.1 instead of 0.3.

People IN THEIR 40s who are double-vaxxed, no waning, no loss of vaccine protection vs Omicron, or triple-vaxxed and back up to 90% protection levels, AND contract COVID-19:

1 in 7,868 will die
1 in 2,174 will end up in ICU
1 in 476 will be hospitalized

People IN THEIR 40s who are double-vaxxed, no waning, no loss of vaccine protection vs Omicron, or triple-vaxxed and back up to 90% protection levels, AND contract COVID-19:

1 in 7,868 will die
1 in 2,174 will end up in ICU
1 in 476 will be hospitalized

People IN THEIR 50s who are double-vaxxed, no waning, no loss of vaccine protection vs Omicron, or triple-vaxxed and back up to 90% protection levels, AND contract COVID-19:

1 in 2,351 will die
1 in 833 will end up in ICU
1 in 227 will be hospitalized

People IN THEIR 60s who are double-vaxxed, no waning, no loss of vaccine protection vs Omicron, or triple-vaxxed and back up to 90% protection levels, AND contract COVID-19:

1 in 703 will die
1 in 303 will end up in ICU
1 in 112 will be hospitalized

People IN THEIR 70s who are double-vaxxed, no waning, no loss of vaccine protection vs Omicron, or triple-vaxxed and back up to 90% protection levels, AND contract COVID-19:

1 in 210 will die
1 in 146 will end up in ICU
1 in 59 will be hospitalized

People IN THEIR 80s who are double-vaxxed, no waning, no loss of vaccine protection vs Omicron, or triple-vaxxed and back up to 90% protection levels, AND contract COVID-19:

1 in 56 will die
1 in 457 will end up in ICU
1 in 35 will be hospitalized

THIS is why controlling case numbers matters. And also why people should think long and hard about socializing with people they don't live with indoors right now.

Now I'm going to walk through what daily case numbers will look like with Omicron, using Ontario as an example, since we're likely at nearly 100% of infections caused by Omicron right now.

The most recently reported estimate from @COVIDSciOntario is that Omicron cases are doubling every 2.8 days. Let's round that up to 3. Let's also assume that the fairly light restrictions recently announced don't have an immediate effect on people reducing contacts b/c Christmas.

@COVIDSciOntario With no slow down, by Christmas day about 0.16% of Ontario population will be getting infected each day. If things don't slow down from Christmas to New Year's, here's what it would look like-ish.

Dec 25 0.16% pop infected (new infections)
Dec 26 0.21%
Dec 27 0.26%
Dec 28 0.32%

@COVIDSciOntario Dec 29 0.43% pop infected
Dec 30 0.54%
Dec 31 0.64%

Add all those up: 2.56% of ON pop infected from Christmas to New Year's.

That's probably about how many people were infected in the entire first wave in Ontario BTW.

@COVIDSciOntario Now for more assumptions. First, let's assume that those infections from Christmas to New Year's happen across all age groups, because of family and social mixing that that time of year.

@COVIDSciOntario What I really hope is that people with higher risk family and friends will actually avoid putting them at risk over Christmas week by not socializing in person indoors, even with N95s and RATs. It's too risky right now.

Nevertheless, let's assume everyone mixes with all age groups as usual, under the assumption that they're well protected.

What's the population age structure of Ontario? Here are the StatsCan July 1, 2021 estimates.

Under 40: 9,137,380 people (55% of pop)
40-49: 1,855,340 (11%)
50-59: 2,019,276 (12%)
60-69: 1,813,493 (11%)
70-79: 1,181,151 (7%)
80+: 674,976 (4%).

Now let's assume 2.56% of each of those age groups is infected. How many infected people is this?

Under 40: 233,917
40-49: 47,497
50-59: 51,694
60-69: 46,425
70-79: 30,237
80+: 17,279

By New Year's eve, if we don't slow spread.

Have to go fill up birdseed outside. BRB.

Birds were yelling at me. We have about 30 evening grosbeaks right now, on top of the usual 10-12 blue jays, hairy woodpeckers, countless chickadees and nuthatches, and on cold days, a collection of diverse, hungry sparrows and sometimes grouse. 30 lb of seeds/week at moment.

Alright, so using those estimated infection numbers for each group from xmas day to new year's eve, and the infection fatality, ICU admission and hospitalization rates above, what do we get?

Let's be very conservative and assume everyone 40% is double-vaxxed (100% vax rate), and that Omicron does NOT reduce vaccine protection against severe infections below the normal 90%.

How many people in their 40s would be expected to die from breakthrough infections contracted from Dec 25-31 in Ontario?

47,497 infections:
1 in 7,868 odds death: 6 deaths
1 in 2,174 odds ICU: 22 ICU
1 in 476 odds hospitalization: 100 hospitalized

What are expected severe outcomes of breakthrough infections contracted by people in their 50s from Dec 25-31 in Ontario?

51,694 infections:
1 in 2,351 odds death: 22 deaths
1 in 833 odds ICU: 62 ICU
1 in 227 odds hospitalization: 228 hospitalized

What are expected severe outcomes of breakthrough infections contracted by people in their 60s from Dec 25-31 in Ontario?

46,425 infections:
1 in 703 odds death: 66 deaths
1 in 303 odds ICU: 153 ICU
1 in 112 odds hospitalization: 415 hospitalized

What are expected severe outcomes of breakthrough infections contracted by people in their 70s from Dec 25-31 in Ontario?

30,237 infections:
1 in 210 odds death: 144 deaths
1 in 146 odds ICU: 207 ICU
1 in 59 odds hospitalization: 513 hospitalized

What are expected severe outcomes of breakthrough infections contracted by people in their 80s from Dec 25-31 in Ontario?

17,279 infections:
1 in 56 odds death: 309 deaths
1 in 457 odds ICU: 38 ICU
1 in 35 odds hospitalization: 494 hospitalized

Add all these up, and you can see that unless we slow spread IMMEDIATELY the conservative estimate is that in Ontario we'll see 547 deaths, 482 ICU admissions and 1,750 hospitalizations from infections contracted between Christmas Day and New Year's eve.

We won't see most of these severe outcomes until January, because hospitalizations, ICU admissions and deaths lag, hospitalizations by 1-2 weeks, depending on age group, deaths by 4 weeks post Xmas week because they happen later and reporting is quite badly delayed.

This is ON, this is conservative. For other provinces it's not a matter of if but when with Omicron, and how stringently people limit contacts, starting IMMEDIATELY.

My biggest fear--that many of us hope to have a fairly normal holiday and THEN hunker down. That's too late.

Considering that fewer than 5-10% of Ontarians are boosted, these estimates are likely unrealistic. If Omicron reduces vaccine protection against severe outcomes from 90% to 70%, these estimates above may be nearly 3 times higher. The problem is, we can't wait for confirmation.

I was next going to factor in estimated severe outcomes in ON for xmas week among unvaxxed people in each age group, but I have to finish marking and paper reviewing. But estimated numbers will be higher w/ unvaxxed outcomes. Also, infections will spread faster among unvaxxed.

A bientot. I don't think I'll stop talking about this over the next 2 wks, even if I'm on vacation. It's like watching an accelerating train about to make a hairpin turn in the mountains, while everyone in the dining car is enjoying food and drinks and brightness and camaraderie.

P.S. @COVID_19_Canada is still doing free, anonymous evening Zoom Q&A sessions and workshops to help people talk to others about vaccination. You can sign up at link below.

I'll be doing most sessions through the holidays, if you want to talk more.

covid19resources.ca/public/vaccine…