Welcome to Plugging the Gap (my email newsletter about Covid-19 and its economics). In case you don’t know me, I’m an economist and professor at the University of Toronto. I have written lots of books including, most recently, on Covid-19. You can follow me on Twitter (@joshgans) or subscribe to this email newsletter here.
Almost all Covid-19 testing and screening requires not being at home. But you don’t need to be a rocket scientist to know that being able to screen at-home is likely to be the most efficient means of on-going screening. However, public health officials do not trust people to do this — something that I have written about before.
The evidence at the moment is that people can administer at-home screens pretty well. This is from Nature:
There are differences but even these are masked by the fact that all of these start to be above 90 percent when you take into account viral load. In other words, there is no real competency concern.
There are two trust issues. First, when you test positive, you might want to conceal that fact. However, there are two things pushing you in the direction of not concealing a fact — that you want to get treatment and that you actually don’t want to harm others. Against this is the fact that you might feel you are now safe. But people who might act on this third effect are the same sort of people who likely were worried about the first two effects beforehand. For this reason, I am not sure whether this is really a concern.
That said, if it was a concern, how would you deal with it? One way is through penalties. If we give people screens and then it turns out later they have infected someone, we might punish them. That sounds harsh but this is something we used in the AIDS toolkit so it is not unprecedented. Another way is through verification. We presume people positive unless they can prove they are negative.
That verification option also comes up with respect to vaccinations and also would be useful if we had good records about past Covid-19 infection. But we do not actually have a great way of allowing people to verify their health status without compromising the privacy laws of many countries. One organisation — The Covid-19 Credentials Initiative — has been looking to solve that.
I can imagine there being some IT or maybe even blockchain solution to this. But in their absence we need to rely on some form of self-reporting.
Even self-reporting can be made more likely to work. For instance, we can issue people tests and when they report results they have to register the test and then use an app to report results. I can imagine a situation where, before you open a test, you have to scan a code that cannot be scanned after it is opened. Then you take the test and there is a code attached to the result which is imaged and then uploaded. In this way, you can have verification but a really determined person would have to work hard to get around it. Importantly, it is going to be hard to find a way of getting a negative result verified if everyone in your house is infected. One suspects, therefore, that with a little thought, this trust and verification issue is not an impediment to at-home screening.
The other trust issue is the one that, I suspect, most confounds public health officials. This is where people screen negative and believe, therefore, they can go out safely and not harm others. Let’s start with the obvious: suppose screens had a false negative rate of 0% meaning that if you screen negative, you are negative. Then surely allowing people to go about their business is exactly the point. Now here I suspect some public health officials will actually still object and worry that people moving around may still become infected. This is true but if screens are regular, then we can still break chains of transmission.
If screens are not perfect — and they aren’t — then there is a risk that someone who is infectious could go around not taking care and, moreover, others believing they are not infectious similarly don’t take care. You know, as they might do in normal life. This is all possible. But surely if screens are regular, these situations will be minimised. What I have not seen is a good analysis that shows that somehow giving people the ability to de-risk themselves will likely lead to a significant problem especially if we have some modest negative verification in place and a regular regime. (I am happy for anyone to point one out to me).
Thus, we are in a situation where we don’t have at-home screens because individuals are not trusted to deal with better information about themselves. Apparently, they would much rather have everyone believe that they and others are much riskier than they actually are. I can see that when there is no way of getting that information. But when the information is available that improves our ability to measure risk by many orders of magnitude, basing a critical policy on mistrust without evidence seems to me to be very risky.