I tried to give a tentative explanation of the herd-immunity strategy. Here are some tough questions about it from someone who is extremely well qualified to ask them. 1/
To these I would add a further question, partly prompted by @andrejbauer. Back-of-envelope calculations suggest that to achieve herd immunity in, say, six months would not be possible without overwhelming hospitals, and therefore having a high death rate. 2/
It might be possible to reduce the death rate quite a lot by getting vulnerable people to self-isolate for their own protection, but it still wouldn't be pretty. 3/
So it looks as though the following three goals are incompatible.
(i) Achieve herd immunity.
(ii) Get life back to normal(ish) before next winter.
(iii) Avoid overwhelming hospitals and thereby substantially increasing the death rate. 4/
(i) Achieve herd immunity.
(ii) Get life back to normal(ish) before next winter.
(iii) Avoid overwhelming hospitals and thereby substantially increasing the death rate. 4/
If you want to see the working (again with very crude numbers), if 40,000,000 people get it, and 5% need hospitalization, that's 2,000,000. To spread that out over eight months, say, makes 250,000 per month. If each person needs two weeks, that's about 125,000 at any one time.5/
The total number of hospital beds in the UK was (I see from the web) around 167,000 in 2017, so we could only just cope even if hospitals were entirely devoted to treating the coronavirus and had all the equipment and personnel they needed, which of course they wouldn't. 6/
To put these numbers into further perspective, Italy has so far had about 15,000 cases in total, and its hospital system was overwhelmed some time ago. 7/
It may seem as though I am contradicting what I said before, but I wasn't trying to come to a definite conclusion either in my previous thread or this one. Rather, I've been trying to explore the numbers in the hope of understanding what is going on, and thanks to Andrej ... 8/
my understanding has improved (not the first time he's done that). I also hope that doing these mental calculations publicly may help others understand, but I stress that I should not be taken as an authority figure here: my working is there to be checked and criticized. 9/
I personally think that if something has to go then it should not be (iii). So I still agree with my previous tentative conclusion that drastic measures will be needed once hospitals are at 5-10% of the number of coronavirus patients they can cope with. 10/
But I don't see how herd immunity can be built up (without a vaccine) in a reasonable time without catastrophic consequences. 11/
How does the maths work out if we don't try to build up herd immunity but instead try to wipe out the disease? Then it's easy: the number of cases is doubling every two or three days, so every two or three days doubles the size of the task. So the sooner we act, the better. 12/
The difficulty is that we almost certainly can't wipe out the disease completely, so we'd have to accept major economic damage (which itself costs lives) and major changes to our lifestyles for a long time, or else the problem would just start all over again. 13/
One strategy would be to accept the damage until a vaccine comes along, but that would be a huge thing to accept, possibly to the point where it threatened things like food security, social cohesion, etc., though perhaps we would get through with a wartime spirit. 14/14
