We all learned a bit of epidemiological jargon over the last year, hey?
The term ‘infection fatality rate’ means:
. . . the proportion of deaths among all infected individuals, including all asymptomatic and undiagnosed subjects. It is closely related to the CFR [case fatality rate], but attempts to additionally account for inapparent infections among healthy people.
The case fatality rate means the death rate among those diagnosed with the disease and will necessarily be higher than the IFR.
I wanted to know: overall, if you get infected with Covid, what are your chances of survival? I saw a big argument about this online with some saying it was way over 1% and some saying it was way less.
Let’s get to the bottom of it.
You’d think the agreed figure would be plastered everywhere but it took some searching to find a meaningful answer.
As you can see, there’s quite a spread. Locations with higher death rates per million also, unsurprisingly, reported a higher IFR.
The median IFR was 0.27% but the range of ‘uncorrected estimates’ was 0.01 to 1.63%.
I might stop here and say, there you have it, 0.27% is the answer. But the range still troubles me. It begs for an explanation because it’s the same bloody disease – how could it be so much more deadly in some places than in others?
The COVID infection fatality ratio is around 1% in high-income countries, but substantially lower in low-income countries with younger populations . . .
Age-specific IFRs increased from 0.1% and below for individuals under 40 years to greater than 5% among individuals over 80 years
Using these age-specific estimates, the team estimates the overall IFR in a low-income country, with a population structure skewed towards younger individuals, can be expected to be approximately 0.23% (95% prediction interval 0.14-0.42).
In contrast, in high income countries, with a greater concentration of elderly individuals, the report estimates that the overall IFR can be expected to be approximately 1.15% (95% prediction interval 0.78-1.79) . . .
In addition, the researchers did not find evidence that the IFR was higher in regions with larger epidemics.
Toot toot, I called it.
Interesting that all the flash medical resources of developed countries did not outweigh or even much mitigate the impact of having older populations. Up until vaccines, that is.
There’s little benefit for Third World countries to have tight lockdowns and other restrictions because (a) their comparatively young population means the disease will be less deadly, (b) economic disruption may end up costing more lives among those already near poverty, and (c) trying to reduce infections until a vaccine comes along makes no sense if you can’t afford a mass vaccination program for several years anyway.
That’s where much of jungle Asia is at. There are still restrictions here and there, schools are closed, but I doubt they’ll get the vulnerable vaccinated even five years from now. Source: the outcome of all previous government programs.
In any case, we got the answer we set out to find: Covid’s IFR is about 0.2% in poor countries and about 1.2% in rich countries.
Also keep in mind that Covid is more than twice as contagious as influenza, meaning more sickness and death overall.
Hope that clears things up.
Edit: this study suggests a mean IFR of 0.68%, again with a very wide range between countries:
Conclusion: Based on a systematic review and meta-analysis of published evidence on COVID-19 until July 2020, the IFR of the disease across populations is 0.68% (0.53%-0.82%). However, due to very high heterogeneity in the meta-analysis, it is difficult to know if this represents a completely unbiased point estimate. It is likely that, due to age and perhaps underlying comorbidities in the population, different places will experience different IFRs due to the disease. Given issues with mortality recording, it is also likely that this represents an underestimate of the true IFR figure. More research looking at age-stratified IFR is urgently needed to inform policymaking on this front.
This backs up the Imperial/WHO figure more than it might seem. I’m guessing the two median figures only differ because the second study included more outcomes from developed countries. As to which is more accurate, it hardly seems to matter because the global average IFR is not a useful figure (after all that).
Each nation’s, and individual’s, risk level is determined by age and health. If you’re in a Toronto nursing home, average outcomes for 20-something Indonesian farmers mean nothing, and visa-versa.
In Wednesday’s post we’ll examine a table of risk levels by age that will inform our food-fight on the topic everyone fancies himself an expert on: Covid vaccines.