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Comment by petilon | Hacker News Reader

Sir Patrick Vallance, England’s chief scientific adviser, said the government was looking “to build up some kind of herd immunity so more people are immune to this disease and we reduce the transmission.” [1]

Britain’s chief scientific adviser ... said that about 40m people in the UK could need to catch the coronavirus to build up “herd immunity” and prevent the disease coming back in the future. [2]

Sir Patrick told Sky News that experts estimated that about 60 per cent of the UK’s 66m population would have to contract coronavirus in order for society to build up immunity. [2]

[1] https://www.nytimes.com/2020/03/13/world/europe/coronavirus-...

[2] https://www.ft.com/content/38a81588-6508-11ea-b3f3-fe4680ea6...

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for reference, at this moment there are 21,157 (according to john hopkins map) confirmed cases in Italy, which probably translates to anything between 50k-500k infections total. lombardy healthcare is near collapse and there's 1.5k people dead already. multiplying by 80-800 (best-worst case to get to 40M) left as an exercise to the reader. at that point the government might not only buy all ventilators on the market but also all diggers.

But if the UK government can managed to isolate elder people, and can get those 40M to contain almost exclusively younger people, won't the fatality rate be far lesser?

Even if the fatality rate for non-old people is only 0.2% that's still impressive 80k dead

Possibly, the isolation is not going to be purely age based, but young people that are more susceptible to the disease might be isolated, in that case the fatality rate could drop significantly.

The problem is that in many cases it's hard to know whether you're susceptible until it's too late. It can be an undiagnosed pre-existing condition, or caused by stress (e.g. due to the crisis itself). For many working adults it might not be easy choice to self isolate (must provide for family etc) so many might likely downplay their susceptibility.

And this is all just talking about fatality rate while hospitals still function normally.

> if the UK government can managed to isolate elder people

You also have to isolate young people with preexisting comorbidities such as cardiovascular disease, diabetes, chronic respiratory disease, and oncological diseases.

There is also no guarantee that the immunity will last. You can catch common cold (which incidentally is also caused by a coronavirus) multiple times. We don't know if that's true for Covid-19 as well.

Common cold is caused by hundreds of different rapidly mutating viruses, sometimes infecting you simultaneously, and it's usually a rhinovirus not coronavirus.

It has been studied and determined most people cannot catch the same cold virus again within a short-medium time frame.

Also don't forget many disabled people as well so could be a significant number of young people as well affected.

This is starting to look like a form of eugenics where the old and weak are simply left to die.

The 0.2% fatality rate depends heavily on access to sufficient medical care. If you infect 40 million people at once, you won't have enough hospital beds and the morality rate will skyrocket.

That's why you don't infect everyone at once and you undertake social distancing, working from home, behavioural changes like avoiding gatherings and increased hand washing etc etc. Governments have been saying for weeks that we'll need to 'flatten the peak' of the infection to keep health care needs manageable.

exactly correct and amazingly this is not what bojo says.

Well, they'll die of other stuff because they can't be taken to hospital without infecting them.

I'm not an expert on this, but based on what has been published my understanding is:

1) Fatality rate is based on hospital care being available for people who do get sick. This will include some nonzero percentage of otherwise healthy young people. Some of these patients will need advanced support, including ventilators.

2) Assuming you could contain to 40M young people (likely impossible), if even .5% of them need hospitalization, the UK hospital system will be overrun. (Not even accounting for all the other people who need hospitalization.)

3) Therefore: the low fatality rate assumption in #1 would likely not hold.

TL;DR; the absolute numbers are too big relative to health system capacity.

Younger people are even lesser likely to need intensive care IMHO. So the numbers should be lesser for hospitalisation too.

Try this exercise:

- Google the # of hospital beds in the UK

- Google the # of ventilators in the UK

- Pick your own fraction as to how many are currently available

- pick your own fraction of 40mm that will require hospitalization

- pick your own fraction of 40mm that will require ventilation

- Make your assumptions fit the # of hospital beds and ventilators

I haven't done all the arithmetic, but my gut says you will end up assuming that people in the "young" bucket are all essentially immune to severe forms of the disease. This is at odds with evidence in e.g. France, which would indicate a problem with your assumptions.

This is at odds with what anyone that is remotely looking at the numbers is thinking. It’s really a joke that so many people here are defending the suicidal choice of boris that is going to produce 1M deaths in the best scenario that I can think of unless it changes everything from YESTERDAY, not from now.

Just to clarify: I was not defending the idiotic choice of the UK government. Was helping lay out numbers to show how stupid that decision is.

From the figures, it looks like 10% of young are still severe pneumonia’s [0]. Not all of those require respirators or ITU, but quite a few will. The figures depend _hugely_ on the number of sub clinical/mild infections. The UK experts have public ally said they believe the overall mortality rate is at or below 1%. Given a global mortality of ~3% it appears they are assuming two thirds are so mild they didn’t present for testing. You must assume this is based on some evidence not available to the rest of us, or from some simulation based on other findings.

[0] https://www.nejm.org/doi/full/10.1056/NEJMoa2002032

> From the figures, it looks like 10% of young are still severe pneumonia’s [0].

Sorry, where do you see that in [0]? Table 3 has a pneumonia diagnosis but isn’t broken down by age, Table 1 is broken down (somewhat) by age but only differentiates between nonsevere and severe “disease”?

If you look at table one it gives you numbers and severity by age. Ignore the percentages quoted (that’s percentage of patients by age in certain groups which isn’t very useful) and look at the raw data. 67/550 in the 19-50 age range are severe. So >10% of those in the study. What isn’t known is the proportion of mild cases not included in the study group.

If you look in methodology (search for severity), severity is defined by severity of the pneumonia according to American criteria. So these columns refer to how bad the pneumonia is.

There are roughly 167,000 hospital beds in the UK of any type. At .5%, you'd need 200,000 beds for just covid19 patients, since the numbers for hospital care have been more in the 5-15% range.

Well, good luck?

"The professor of intensive care medicine, who himself heads the ICU of the Rotterdam Erasmus MC, emphasizes that it is not only the elderly who are affected by the corona virus. 'What has mainly made the news is that older people die faster. This is about 2.5% of the entire population, while about 15% of the elderly die. But _more_than_half_ of those patients are under fifty years old. It also includes young people."

The idea is that if the government can infect low risk citizens then they can recover on their own without relying on the healthcare system. It's the high-risk individuals who put load on healthcare, so the proposal is to use the low-risk citizens to build up immunity.

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