This is an odd resource, at least with respect to IFR. I didn't look to see if the CFR section was more reasonable. They don't date the commentary in the IFR section, but it seems like it's mostly March/early April? If so, we obviously know a lot more since then.

> We could make a simple estimation of the IFR as 0.35%, based on halving the lowest boundary of the CFR prediction interval in Europe.

I mean, sure, maybe an ok guess way at the beginning.

> In Swine flu, the IFR ended up as 0.02%, fivefold less than the lowest estimate during the outbreak (the lowest estimate was 0.1% in the 1st ten weeks of the outbreak).

We simply weren't doing the surveillance needed for the 2009 H1N1 pandemic during the pandemic to have reasonable estimates for quite a while. We are doing much more of that for Covid - we have serology studies, and we have fairly accurate death numbers (at least in some countries), the key pieces to put together more robust IFR estimates. We didn't have those for H1N1. I also find it a little odd this page just generically references it as Swine flu, vs being specific about it being the 2009 iteration of it. I'd expect that from a news outlet, not an Oxford associated group.

> In Iceland, where the most testing per capita has occurred, the IFR lies somewhere between 0.03% and 0.28%.

Iceland contained their outbreak (yay!), and had very few cases overall, and just 10 deaths. Their CFR is 0.28%. Given their massive amounts of testing, it's hard to understand where the 0.03% comes from (and, obviously, is wildly low). But mostly, there were so few cases in Iceland that's it's hard to draw many fatality rate conclusions.

But mostly:

> Antibody testing will provide an accurate understanding of how many people have been infected so far, and permit a more accurate estimate of the IFR.

> *Estimating CFR and IFR in the early stage of outbreaks is subject to considerable uncertainties, the estimates are likely to change as more data emerges.

Seems to be consistent with this having been written up in March/early April. Since they haven't updated it, and the reasoning even at the time was fairly poor, this doesn't seem a useful resource (at least for IFR).

The COVID IFR is very strongly dependent on age. The U.S. median age is 38, the UK median age is 40, and the world median age is 30.

8-10 years difference in median age is an enormous difference in the proportion of 70+ in the population, and an even bigger difference in 80+. This is a huge part of the reason that you haven't seen the death toll be nearly as high in developing countries as in developed countries. In general, developing countries have a much younger population.

Sure that's a factor, but how do you account for Ecuador with a median age of 28 and a higher per capita death rate than the UK or USA? Ecuador has less healthcare capacity but that can't account for the whole difference. Conversely, Sweden has a median age of 41 and a lower death rate.

It's a statistical association, not a rule. I can't say specifically why those two countries have had the results that they have, but the age dependence holds both at the individual and country levels overall. That also doesn't mean that you can't find a 100 year old survivor and a 20 year old that dies from it.