COVID-19: The effect of a ‘circuit-breaker’ lock-down

It is hard to see the future, but with calls for a ‘circuit-breaker’ lock-down ringing around, it is worthwhile to try to anticipate the effect of such a policy.

During the previous lock-down, key indicators of prevalence of the epidemic

• the rate of daily positive tests,
• the rate of daily hospital admissions, and
• the rate at which people were dying…

… all fell, roughly halving every 21 days.

We can estimate that a ‘circuit-breaker’ lock-down might be as effective at suppressing the virus as that national lock-down was in May and June.

Based on that assumption, the graph below shows the likely effect on the key indicators of ‘circuit-breaker’ lock-down.

Click for larger version.

The term ‘circuit-breaker’ is mis-leading

The term ‘circuit-breaker’ implies that that it will have an immediate and dramatic effect.

But if the policy is as effective as the spring lock-down, then this will not be the case – the key indicators will halve every 21 days.

If we had a 21 day lock-down, then after it was over, it would take only 15 days for key indicators to return to their current values.

So 36 days down the road – i.e. late November – we would likely be back where we are now.

My Conclusion

• The only thing that has demonstrably reduced the prevalence of the virus is a lock-down such as we had in May and June.
• But even that spring lock-down was not very effective, reducing viral indicators with a halving time of 21 days.
• IMHO we need a series of planned lock-downs – roughly 2 weeks on and then 3 weeks off – which will maintain the viral prevalence at its current level.
• We would need to live like his until the spring when a vaccine will presumably become available.
• The cost is terrible. But the alternative – mass deaths and then a lock-down – is worse.

As I pointed out previously (link), the current state of play and the options open to us are similar to what was predicted by Neil Ferguson back in March.

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Details

The graph above has a logarithmic vertical axis and shows the situation in the UK since the start of the opening up at the start of July with regard to:

• The daily rate of Positive Test Results
• Hospital Admissions
• Deaths per day

The data were downloaded from the government’s ‘dashboard’ site.

• Positive tests refer to Pillar 1 (hospital) and Pillar 2 (community) tests combined – not the Pillar 4 tests from the ONS survey.
• The deaths refer to deaths within 28 days of a test.
• Hospital admissions for the UK nations combined

All curves are 7-day retrospective rolling averages of the data since July.

The graph shows the data alongside exponentially decreasing and then increasing trends shown as dotted lines.

• The declining trends correspond to quantities halving every 21 days.
• The increasing trends correspond to quantities doubling every 15 days.