Lockdown Controversies

Ever since the first lockdowns were imposed to try to slow down and control the exponential spread of Covid-19 were imposed in March 2020, there have been many counter arguments and objections. The general argument is that lockdowns are extremely expensive not only in terms of the economy but also because of other deleterious effects on health, education and general social welfare and that therefore lockdowns are an overreaction. 

Cost/Benefit analyses have claimed to show that the cost of lockdowns is far greater than the benefits. The problem in most of these comparisons is that they use numbers for Covid cases and deaths that are after lockdown, since most countries have imposed lockdowns. This comparison needs to be done against the Covid cases and deaths that would have occurred if there had not been a lockdown.

To do this comparison, here is a spreadsheet that shows the difference between lockdown and no lockdown. It is based on actual Covid case numbers (shown in blue) from the time lockdown was imposed in Canada.

The first block (in green) shows how cases would have grown with No Social Distancing measures.

R(t) is the reproduction number, the average number of people that are infected by someone who has the virus.

On Mar 22,
New Cases are 2.8 * 188 = 526
Total Cases rise to 526 + 252 = 778
And so on for each week. That’s all there is to this spreadsheet, pretty simple math.

Under Lockdown (pink block), R(t) reduces from 2.8 to 0.9 in May.
For a simple model, this matches the Actual data (yellow block) pretty well.

The difference between Lockdown and No Social Distancing is pretty dramatic.
On May 17 there are over 3,093,570 Total Cases of Covid if nothing is done, but only 74,100 with lockdown.

Note that Lockdown is the only social distancing measure that will reduce an R(t) of 2.8 to less than 1, which is necessary to slow the exponential growth.
https://wwwnc.cdc.gov/eid/article/27/2/20-3412-f5

You can see why so many countries went into Lockdown in March 2020. If you were a leader of a country and your health experts showed you these projections, even if you didn’t understand the math and weren’t sure of the result, would you have risked 3,000,000 cases of Covid that would have completely overwhelmed the hospitals versus 74,000 cases by not calling for a Lockdown? Most responsible leaders did not take that risk, with a few exceptions like Bolsonaro in Brazil and several U.S. state governors like DeSantis in Florida.

Another argument against Lockdown uses Covid statistics and excess mortality graphs to show that Covid-19 is no worse than a bad flu season. We don’t impose lockdown for flu, why do it for Covid?

Again, these arguments use existing Covid statistics, not what would have happened if there had been no lockdown.

Let’s look at the numbers.
A bad flu like H1N1 (Swine flu 2009) had an R(t) of 1.4. Here is the spreadsheet.

So Covid is a lot worse than a bad flu. After 9 weeks there are over 3,000,000 Covid cases versus 13,000 flu cases. Again, this is simple high school math.

References

Actual weekly case data (blue)
https://ourworldindata.org/coronavirus-data-explorer?zoomToSelection=true&minPopulationFilter=1000000&time=2020-03-02..latest&country=~CAN&region=World&casesMetric=true&interval=weekly&smoothing=0&pickerMetric=location&pickerSort=asc

Reproduction number for Canada
https://globalnews.ca/news/6917781/coronavirus-reproduction-number-canada/

Reproduction number for H1N1 Flu
https://www.livescience.com/covid-19-pandemic-vs-swine-flu.html