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.



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.


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