Coronavirus: Eradication and Herd Immunity

Just a quick post about what a government can and can't control in fighting the virus.

First imagine a country that has complete control of its borders (perhaps it is an island) and would not suffer greatly from cutting off international travel. This country does not have to face any external constraints. If it has the domestic capacity to eliminate the virus quickly, it can do so without reinfection from outside.

However, domestic capacity is not a given. Governments vary in perceived legitimacy and constitutional powers, and populations vary in cohesion and compliance. More on this later.

Now consider a country that relies, to a significant degree, on international travelers, or that doesn't fully control its borders. This country can perhaps crush the curve in the first instance, but it may face new outbreaks if its neighbors/visitors come from countries that choose not to eliminate the virus.

This may change the calculation on whether to take the "Swedish" approach or the one adopted in much of east Asia (but not Japan). The great downside of the "Swedish" approach is that it means accepting a large number of deaths that may otherwise be preventable. But the upside is that it achieves "herd immunity" relatively quickly and therefore inoculates the society against further outbreaks. A country that faces constant reintroduction of the virus from external sources may find the Swedish approach relatively palatable, whereas a country that does not may prefer to eliminate the virus.

Similar logic applies if you have an internal source of infection that cannot be addressed. This might be true for any of a number of reasons, some of which I already mentioned. In the U.S., political power is fragmented and some states have already dropped their efforts at mandatory social distancing. (In one case, Wisconsin, the government wanted to continue the restrictions but the state's courts ruled them illegal.) In that context, it seems to be a daunting political/legal challenge to eradicate the virus.

It is also less attractive a goal than it might be in a place like Taiwan or Korea. A major advantage of eliminating the virus is that ordinary behavior becomes feasible again. Sweden is paying a heavy economic price for its approach, in that its economy is hobbled by the voluntary social distancing that its population has adopted. The big east Asian economies (again, barring Japan) are doing a lot less social distancing now that the virus is mostly eliminated. But as Korea's recent experience shows, this makes countries vulnerable to new outbreaks, and if those outbreaks happen often enough, it no longer makes sense to abandon social distancing, and one of the major advantages of the eradication model is lost.

Another way of thinking about this is that the desirable outcomes are fairly bimodal. If a society truly gets rid of the virus and keeps it out, then it can enjoy normal behavior. If a society truly gains herd immunity, then likewise. In between is a vast gray area that is not nearly as variegated as commentary would seem to suggest, because at any moment an outbreak can come.