All models are wrong, but some are useful.

George Pelham Box


The US and the UK are both in the process of reviewing their strategies in response to the coronavirus. On March 13 2020, President Donald Trump moved from his previous policy of dismissing the threat from the virus to announcing a state of national emergency. And on March 14, the UK government announced a series of measures which suggest that it may be moving away from its previous laissez-faire strategy.

Of course, there are thousands of variants, but as the diagram below indicates, there are only four generic strategic approaches:

  1. the laissez-faire strategy;
  2. the isolate the vulnerable strategy;
  3. the retard the progress of the virus strategy;
  4. the lockdown and eliminate strategy.

What new strategy should the US and UK governments adopt? There is no good option. Every option has both some significant benefits and some very serious drawbacks. Most countries have chosen the lockdown and eliminate strategy – and this is what the World Health Organisation recommends – this post explains why.

Most of the numbers in this post relate to the USA; if you want to see a similar analysis for the UK, this earlier post will be interesting.

The laissez-faire strategy

Most countries have adopted significant policies to avoid rapid mass infection. Until recently, the US and the UK had done relatively little. The UK’s chief scientific advisor suggested that we should follow a different path: hoping for 60% of the UK population to get the virus to build herd immunity. In the US, President Trump had previously claimed that, “we think we have [the virus] very well under control.”

Both the US and the UK seemed to be following the laissez-faire strategy. And that strategy does have some enormous advantages – and also some horrendous costs.

The Pros are speed and subsequent immunity

With few preventive measures in place, the UK experienced growth in number of cases from 13 on February 26, 2020 to 459 on March 12, which suggests that each infected person can infect around 0.25 others per day. On the basis of that rate of potential infection, the build-up of herd immunity in the US, if it followed the laissez-faire strategy were, could look like this.

Within about 15 weeks, the virus would largely have run its course and significantly more than 60% of the US population would have developed herd immunity (assuming of course that recovery implies immunity and that the virus does not mutate in the period shown).

The population would be, of course, smaller than today but as the UK journalist Jeremy Warner wrote in the Daily Telegraph,

“Not to put too fine a point on it, from an entirely disinterested economic perspective, the COVID-19 might even prove mildly beneficial in the long term by disproportionately culling elderly dependents.”

Rather more convincingly, once the herd immunity exists (assuming that lasting immunity does indeed result from exposure and recovery), the threat from the virus is over. Even if visitors from another country reintroduced it, too many people would be immune for it to spread. This is a possibly significant advantage over any strategy which successfully contains the virus.

The Cons are that 2 million could die

According to the John Hopkins dashboard, as of March 13 2020, there were 135,382 identified cases of the virus globally. Of these, 4,981 have died and 69,645 have recovered. That is a death rate so far of 3.7% and a recovery rate so far of 51.4%. Over time, the recovery rate can be expected to grow; hopefully not the death rate. In the UK, the Chief Medical Officer has estimated the true death rate to be 1%. At first glance, this seems in conflict with the facts, but since many of the infected will be asymptomatic or have very mild symptoms, we may never know their true numbers and the true death rate could indeed be well below 3.7%.

To get herd immunity in the US, with 60% immune, would mean infecting almost 200 million people. And assuming a conservative death rate of 1%, almost 2 million deaths would result. If, as some others have suggested, herd immunity requires something more like 80% to be infected, the total number of deaths would far exceed 2 million.

In addition, if this is achieved quickly, then the spike in workload for the US Healthcare system would look like this.

This is dramatically more than the hospital system would be able to cope with. The practical reality is that few of those even with severe symptoms would be able to be hospitalised; they would have to be cared for at home – and their survival rate would almost certainly be lower as a result.

To put this death toll into context, here are some other noted killers in the US.

This would make the coronavirus far more deadly than the Spanish ‘flu – indeed if the US were to follow the laissez-faire strategy, it could be worse in terms of mortality than all these previous events combined.

The Isolate the Vulnerable strategy

An interesting variant on the laissez-faire strategy has been considered in the UK. In this strategy, among other measures, the elderly and vulnerable were to be quarantined in their homes for 4 months. If this could be achieved, while achieving herd immunity in the rest of the population and eliminating the virus, then (assuming no reinfection), the death toll would be far lower.

Experts have questioned the realism of these assumptions in practice. But for the sake of argument, we could assume that:

  • the overall 1% death rate is made up of, say, 4% death rate in the vulnerable population and only 0.25% death rate in the robust population;
  • the vulnerable can be completely quarantined until herd immunity is reached in the exposed population;
  • the quarantine is continued until the virus has been wiped out of the exposed population so that the vulnerable can be safely released.

On those questionable assumptions, the result might look like this.

The results are far better than for the laissez-faire strategy. But still, in terms of US deaths, this would be worse than the two World Wars combined. And given the grave uncertainty around the assumptions, these results almost certainly understate the cost in lives.

What is the alternative?

The principal alternative is to do what the rest of the world is doing – impose serious restrictions to reduce the rate of spread of the virus.

The chart below summarises the predicted number of deaths in the US at different rates of infection (potential number of people infected by each infected person per day). As noted above, the evidence so far suggests that on the laissez faire strategy each infected person can infect around 0.25 others per day. The chart shows how critical it is to get that number down if we want to avoid millions of deaths.

As we saw above, if the potential infectivity rate does not change, we could easily have well over 2 million deaths in the US. If it does, of course, the death toll could be very different. And there are two variants of this strategy:

  • Retard the progress of the virus through the population in order to prevent the healthcare system being overwhelmed, and conceivably to give time for a vaccine to be developed;
  • Lockdown the system to such an extent that the virus is eliminated before it kills significant numbers.


Retard the progress of the virus to allow treatment

If we can reduce the potential infectivity rate to under 0.15 per person daily, the spike will be flattened dramatically.

The peak number with serious symptoms if we follow this strategy is around 22,000 as against approximately 940,000 hospital beds in total and 100,000 Intensive Care Unit beds – massively disruptive but not completely inconceivable.

The number of deaths, theoretically at least, is dramatically reduced to below 350,000. But the overall process takes more than two years, during which significant restrictions on the economy and on individual freedom are necessary. The level of economic damage done in this strategy is hard to assess, but it is reasonable to suppose that in itself, it might cause a significant number of additional deaths.

Also, the number of people who have become immune is far short of any estimate of what is required for herd immunity. So if there were to be any relapse, as there was with the Spanish ‘flu, a second wave of infections could sweep through the population.

If a vaccine could be found early in this process, the retard strategy would be highly effective. If not, it may be impractical.

Lockdown the system and eliminate the virus

But if we can get the potential infection rate down to 0.1, then the whole thing could be over in about 13 weeks.

In this scenario, the total number of deaths is negligible. Of course it shares with the retard strategy the disadvantage of not having built herd immunity, so for these numbers to be meaningful once the lockdown ends, there would need to be quarantine for visitors from any country which had not eliminated the virus. This is the policy which Hong Kong has now adopted.

On the basis of these numbers, the lockdown strategy seems by far the best. And the practical evidence from around the world is that countries that act fast and drastically, do indeed have a far lower death rate. The Director General of the World Health Organization said,

“Let me be clear: describing this as a pandemic does not mean that countries should give up. The idea that countries should shift from containment to mitigation is wrong and dangerous….Countries that decide to give up on fundamental public health measures may end up with a larger problem, and a heavier burden on the health system that requires more severe measures to control.”

So what we need the governments of the US and the UK to do now is to put us on an emergency 13-week lockdown of all non-essential public contact. Critical National Infrastructure, of course, must continue to function, but most businesses should ask employees to work exclusively from home; and those which cannot do that – and which are not part of the Critical National Infrastructure (such as food and pharmacy retail) should close temporarily.

To make this possible, of course, government will need to provide financial support to citizens and business owners. Germany, for example, has just announced unlimited credit to support its businesses during their lockdown procedures.

And an emergency 13-week universal basic income might be a key plank of such an idea. Without something along these lines, many people could not afford to self-isolate, as existing provisions run the risk of being both inadequate and too slow, leading to non-compliance with the lockdown measures and a failure to contain the virus. The cost, of course, will be enormous – of the order of $1 trillion. But that is less than one third of the Federal Reserve’s QE Programme after the Global Financial Crisis.

And it could easily save 2 million American lives.

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