What does it imply if this Oxford-based study of the UK already indicates that 1/2 the population is already infected with COVID-19?

> https://amp.ft.com/content/5ff6469a-6dd8-11ea-89df-41bea055720b

> https://www.dropbox.com/s/oxmu2rwsnhi9j9c/Draft-COVID-19-Model%20%2813%29.pdf?dl=0

> The new coronavirus may already have infected far more people in the UK than scientists had previously estimated — perhaps as much as half the population — according to modelling by researchers at the University of Oxford.

> If the results are confirmed, they imply that fewer than one in a thousand of those infected with Covid-19 become ill enough to need hospital treatment, said Sunetra Gupta, professor of theoretical epidemiology, who led the study. The vast majority develop very mild symptoms or none at all.

If 1/2 are infected then herd immunity is already reached and they only have to wait for the progression of the illness to play itself out. The document in the dropbox link shows concise details of the parameters of the stochastic compartmental model they are using

![](https://imagizer.imageshack.com/img924/413/ZdzB9O.png)

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The study mentioned above has issues. It may take a while to shake out, so look at the following Twitter thread and follow up to see what the eventual interpretation settles down to

In the UK, it's a battle between the Imperial College model and the Oxford University model. Essentially, the Imperial model says that we are at the initial acceleration of the logistic function with a high potential lethality, while the Oxford model says that we are in the last few doublings of the logistic function as it nears the 50% inflection point, and we are only seeing a critical care increase because the overall lethality is very low. So criticality is \$$N \times p \$$ -- Imperial says *N* is still low, while *p* may be large while Oxford say it is just the reverse.