I want to respond to this thread, respectfully disagreeing with @ASPphysician that we should no longer use AstraZeneca in Canada.

Aside from a critical math error, there is an assumption which skews his opinion.

And a few other important things I feel were left out.

…1/11 https://twitter.com/aspphysician/status/1391076247883632645

First off, the incidence of ICU admission from AZ vaccine ranges from 0.787-3.85/100,000 as opposed to what is reported in Dr. Morris’ thread.

I calculated this using the same estimates of risk from @COVIDSciOntario that he used: 1:26,000 to 1:127,000.

…2/n

A big false assumption is comparing this risk of ICU from AZ to just one week of COVID ICU risk.

Personally, I got my AZ vaccine on April 20th; the earliest I can book Pfizer in my region is May 23rd. But let’s still assume a two week lag.

…3/n

Demographically, age 40-49 make up 15.7% of Ontario’s population.

And 0.562% of those who get COVID in this age group end up in the ICU.

…4/n

Now remember: The risk of ICU from AZ is between 0.787 to 3.85 per 100,000.

To have the same risk of ICU from COVID, the number of cases seen in two weeks would have to be between 140 to 685 per 100,000.

…5/n

This works out to between 70 to 343 weekly cases per 100,000 for the risk of ICU to be in the same range as from ICU from AZ.

For ages 50 to 59, it’s between 31 to 154 weekly cases per 100,000.

And 141 to 690 weekly cases per 100,000 for 30 to 39.

…6/n

Where should we STOP administering AZ?

If your 30-39: In any zone with less than 141 weekly cases per 100k

Ages 40-49: In any zone with less than 70 weekly cases per 100k

And ages 50-59: In any zone with less than 31 weekly cases per 100k

…7/n

Where is vaccination with AZ definitely advantageous?

If your 30-39: In any zone with more than 690 weekly cases per 100k

Ages 40-49: In any zone with more than 344 weekly cases per 100k

And ages 50-59: In any zone with more than 154 weekly cases per 100k

…8/n

What about the “middle zone”?

This is where I feel you should err on the side of the vaccine.

VITT is not transmissible; but COVID is.

…9/n

So where do the numbers show AZ is a good call:

Ages 50-59: In 26 of 34 Ontario public health units

Ages 40-49: In 16 of 34 health units

Ages 30-39: In 7 of 34 health units (54.4% of Ontario’s population)

…10/n

In short, getting a shot of AZ before Pfizer is beneficial in many places.

And by taking a shot of AZ, you’re leaving a dose of Pfizer to someone under 30, and helping that person get vaccinated sooner.

Get AstraZeneca if you’re…

Age 30 to 39 : Your region is above 141 weekly cases per 100,000.

Age 40 to 49 : Above 70 weekly cases per 100,000.

Ages 50 to 59 : Above 31 weekly cases per 100,000.