The question raised about whether or not shelter-in-place controls can be lifted by Easter has had me think about that possibility, and specifically what the path to get there might look like. It’s fine to raise such possibilities, if not only to have us check our assumptions, but once done, unless executable, they are pointless.
It seems that there are three paths forward:
- Do nothing
- Shelter in place
- Partial Opening
The Do Nothing approach might also be referred to as an approach to develop Herd Immunity (see What is herd immunity and can it stop the coronavirus? – MIT Technology Review). In this approach the community eventually reaches a point where so many people have been infected, and thus have become immune, the outbreak fizzles out on its own as the virus finds it harder and harder to find a susceptible host. Longer term, vaccinations will result in herd immunity. The key assumption here is that by becoming infected one becomes immune. While this is likely, it has yet to be confirmed.
For this approach to work, and for current data around COVID, between 50-60% of the population needs to be immune. This of course implies that 50-60% of the population needs to have survived the illness. But not everyone does survive. A death rate of 1% implies that 1% of those infected will not make it. If 50-60% of the population is infected then that means approximately 1% of half the population will succumb to the virus. For Canada with a population of about 37 million, that mean 185,000 – 222,000 people.
At the other end of the spectrum, the Shelter In Place approach seeks to stifle the spread of the virus by preventing it from being transferred to other people. Based on the assumption that the virus is spread through the distribution of virus-infected droplets of the various liquids that we emit from our bodies, and that they can travel no more that 2 meters, keeping that distance apart will prevent the virus from spreading.
Distancing is only one of many methods. We could all wear masks for example, but this may not be practical due to cost and availability. The method widely used is Shelter In Place, where everyone stays at home. The challenge with all these methods is to get compliance. Shelter In Place might be relatively attractive as it is easy to measure. If you’re outside you are not compliant. While historically enforcement of such curfews has proven difficult to enforce, GPS monitoring, drones, and street-side cameras coupled with facial recognition offer technology-based approaches.
These technical solutions are attractive as they reduce resource demand and are likely more effective in their completeness. But such a high degree of monitoring can lead to a sense of the emergence of a police state.
The Partial Opening approach seeks to find a middle ground between the first two approaches. It is the one proposed for an earlier, Easter, timeframe. For this to work, you need to know the risk profile of the individual so you can determine whether they need to remain house-bound and whether they can go out. It also supposes that enough people can go out to be useful. Those with the lowest risk are those people who are immune. Until a vaccine becomes available, these are the people who have been infected and have survived. As the disease is asymptomatic in many, to determine if a person is immune requires testing. Testing, at this time, is unavailable in sufficient quantity to take this path.
Yet, if infeasible at this time, Partial Opening could represent a second phase after Do Nothing and/or Shelter in Place. In both these cases, as time goes on, an increasing portion of the population will have become immune, and thus are able to return to work. But whether the numbers will be there to make sense is another question.
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