Why a SARS-CoV-2 variant that's 50% more transmissible would in general be a much bigger problem than a variant that's 50% more deadly. A short thread... 1/
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As an example, suppose current R=1.1, infection fatality risk is 0.8%, generation time is 6 days, and 10k people infected (plausible for many European cities recently). So we'd expect 10000 x 1.1^5 x 0.8% = 129 eventual new fatalities after a month of spread... 2/
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What happens if fatality risk increases by 50%? By above, we'd expect 10000 x 1.1^5 x (0.8% x 1.5) = 193 new fatalities. 3/
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Now suppose transmissibility increases by 50%. By above, we'd expect 10000 x (1.1 x 1.5)^5 x 0.8% = 978 eventual new fatalities after a month of spread. 4/

2:40 PM ยท Dec 28, 2020

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The above is just an illustrative example, but the key message: an increase in something that grows exponentially (i.e. transmission) can have far more effect than the same proportional increase in something that just scales an outcome (i.e. severity). 5/5
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Replying to @AdamJKucharski
Not if you protect the vulnerable via vaccines or NPIs. If large parts of the population are not seriously harmed by it then every person that gets it and develops immunity reduces the overall risk to the vulnerable. The faster the spread, the less time you need to protect for.
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Replying to @AdamJKucharski
Why would you stop the calculation after one month?
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It's a very rough calculation to show a valid point. However, it doesn't work the longer you do it for. E.g. if you did it for six months (30 cycles of infection) you'd have 267 million deaths and 33 billion infections with the new 'more transmittable' Covid.
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Replying to @AdamJKucharski
Is it true to say 50% more transmissible = 1.5 x R? And if so, would we assume a linear relationship between transmissibility of two strains with a varying R?
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Replying to @AdamJKucharski
difference between 1.1^5 and 1.65^5 is big indeed... 7.6x.... that would be bad news... and I guess we have seen it... exponential growth has proven difficult to grasp for many... positive reactions have allowed deniers to reaffirm their beliefs from time to time
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Replying to @AdamJKucharski
Analysis worthless as unscientific & does not account for the MOST COMMON viral mutations -Non meaningful -Increasing transmissibility AND decreasing case fatality Using CFR from prior strain but projected transmissibility from theoretical new strain is automatically invalid
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Replying to @AdamJKucharski
I am not a math person but does the 978 fatality represent a scenario where the virus and a combined 50% transmissibility and 50% increase in fatality? If that is the case then it appears to me that it doesn't show ONLY50% transmissibility is far worse than 50% fatality increase.
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No, the 978 is only a 50% increase in transmissibility, but the fatality rate staying at 0.8%
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