Thread by @AndreasShrugged

Call me pedantic, but I insist that journalists need to know the difference between case fatality rate, infection fatality rate, and mortality rate when making big statements about Covid. @dwallacewells mixes these up, resulting in an unsupported claim. @NYMag @intelligencer

https://twitter.com/BallouxFrancois/status/1414637864629985283

So the first part is correct, as provided by the source: COVID-19 IFR for children aged 5-9 not higher than 0.001%. Note the same is not true for the younger children aged 0-4 and older ones aged 10-14.
nature.com/articles/s4158…

So what "about one-tenth the risk of flu in that age group"? The source claims a COVID-19 "mortality rate" of 0.009% in Florida and a flu "mortality rate" of 0.01% for the age group 14 and younger. It also says/quotes that 0.009% is "far below" 0.01%(???).
healthleadersmedia.com/covid-19/true-…

First, the age group from the Covid IFR 5-9 age group isn't the same as the age group considered for these "mortality rates". Second, what about the "mortality rates"? Here's where it gets complex. Following the source within the source...

...leads us to a FL report featuring this table. We can calculate a COVID-19 "mortality rate" by adding the deaths (0+3) and dividing them by cases (22218+9357), which indeed yields 0.009(5)%. But that's not a mortality rate, that's a case fatality rate!
floridadisaster.org/globalassets/c…

A case fatality rate (CFR) is larger than an IFR because it counts only cases, not infections; both are larger than mortality rates, which divide deaths by population. This Covid-19 CFR is 9X larger than the Covid-19 IFR we just saw at the beginning. But where's the flu?!

Turns out there isn't a source for the 0.01% flu "mortality rate" that the Covid-19 IFR was compared to. And it's not an actual mortality rate (MR) because FL Health reports an influenza MR of 0.5/100000 or 0.0005%, which is very low as expected from a MR.
flhealthcharts.com/ChartsReports/…

So the 0.01% flu whatever-rate isn't sourced, which means the claim that the flu is worse than Covid at young age isn't validated here! If it's also a case fatality rate, then the comparison to the COVID-19 IFR is wrong because these two type of rates aren't directly comparable.

I think this showed how difficult it is to correctly source a simple yet impactful statement like that - or how easy it is to push an agenda. I haven't even gotten into other studies as additional source. Small reference on the different rates below.
intereconomics.eu/contents/year/…

Aha.