Thread by @syrpis

A (grim) thread on 'herd immunity', and the UK Govt response to the coronavirus pandemic. 1/

There are of course some extreme views, but I think it is fair to assume that the vast majority of people on all sides of this debate want a positive outcome. Quite how a positive outcome is defined may differ. 2/

The main aim is to save lives. But people differ on how many lives it is possible to save. They may also differ on the calculation as between 'coronavirus deaths' and 'other deaths' (eg caused by a prolonged lockdown, a deep recession, etc). 3/

The 'herd immunity' approach is based on the view that it is *not possible* to *stop* the spread of the virus. Instead, all we can do is *slow* the spread of the virus. 4/

It is based on the view that the key is to *slow* the spread, so that the NHS is not overwhelmed, and so that *unnecessary* deaths (of those who can't get access to care because of a lack of capacity) are avoided. 5/

There are several things to think about in relation to this approach. 6/

First, it only works if those who have had the virus are then immune from it (and future strains). That is still, as I understand it, uncertain. If there is immunity, it provides the prospect of 'light at the end of the tunnel'. If not, it doesn't. 7/

Second, and assuming it works, the implications depend - crucially - on the number of people who have had the virus. In this model, the higher the number, the better. The closer we then are to that 'light at the end of the tunnel'. 8/

Sir Patrick Vallance suggested this week that less than 10% of the population have had the virus. More testing would create more certainty. But... if he is right, the promised light is a long way away. 9/

Third, and this is the most important thing, is the view that the virus cannot be stopped and can only be slowed, correct? [This is one area in which 'the science' can help to provide an answer, though from what I've read, opinions are divided.] 10/

Many countries *are* attempting to stop the spread. The WHO is advising that countries should try to stop the spread. New case numbers are falling in many parts of the world, despite the fact that the virus has not spread through the population. See Germany, S Korea, NZ. 11/

Now... it may be that these countries are vulnerable to a second, and a third etc, peak. The fewer cases they have had, the more vulnerable they are. Time will tell. 12/

How does all this feed into the policy response?
13/

An approach based on the view that the virus *will* spread through the population does not mean that social distancing and other measures can simply be lifted; some measures will need to remain in place to ensure that the NHS is not overwhelmed. 14/

I don't know how long it would take for what may be millions of cases to go through the system. Many months, certainly. And, all the while, deaths will continue. But the hope is that 'unnecessary' deaths will be avoided. It's a grim picture. 15/

The alternative also presents huge challenges and difficulties. The alternative means a big, concerted effort, not just to *slow*, but this time to *stop*, the spread of the virus. This time the fewer cases we currently have, the better. 16/

The initial lockdown will need to last longer, in order to reduce new cases 'to a trickle'. Even then, restrictions cannot be easily lifted. The 'containment' phase, in Feb/March, was not conspicuously successful. 17/

So, if we start to lift restrictions, we will have to do things differently. Testing and tracing (on a vast scale) will be needed. I found this analysis very useful:
institute.global/policy/suppres… 18/

This strategy has big implications for (eg): large gatherings, the opening of schools and universities, international travel. It is much easier to see these things happening in a world in which we are trying to *slow* rather than to *stop* the virus. 19/

Ultimately there is a choice to be made.

If it is right that the virus cannot be stopped, the best we can do is to manage its progress. We will be able to return to close to normal more quickly. But there will be a backdrop of deaths - perhaps 100s of thousands. 20/

If on the other hand we do try to *stop* the virus, we will not return to anything like normality. Testing, tracing and monitoring will become part of life. If there are any signs that new cases are increasing, strict(er) lockdown may, once again, be needed. 21/

If this strategy works, we may end up with a coronavirus death toll of (say) 25,000. Missteps along the way may result in a doubling of that total. It may turn out to be futile (think Canute and the tide). 22/

These are the choices which we - and every other country - are facing. Different countries are approaching the challenge differently. We will all learn a lot in the coming weeks and months about what does and does not work. 23/

My grim conclusion is that the months before a treatment and/or a vaccine emerges can be distributed to all, will be difficult. There is no prospect of a quick return to normality.

But... there is an urgent need to articulate what it is that we are trying to achieve. 24/24