I think that it is very hard to do a proper accounting. It is difficult to forsee all the consequences of an intervention; if a parent is sick, they do not work. The other parent may need to stay home too to help out. A double whammy on productivity. The firm employing them takes a hit too, as well as the municipalities and other levels of government depending on tax revenue. Such hits can lead to declines in necessary investment. And this doesn't even account for possible epidemiological effects, which can be highly nonlinear, as infection Cascades can be frequency dependant.