Thread by @NoahHaber

At the risk of getting involved in a discussion I really don't want to be involved in:

Excepting extreme circumstances, even very effective or very damaging policies won't produce discernable "spikes" or "cliffs" in COVID-19 outcomes over time.

That includes school policies.

"There was no spike after schools opened" doesn't mean that school opening didn't cause (ultimately) large increases in COVID cases.

Similarly "There was no cliff after schools closed" doesn't really mean that the school closure didn't substantially slow spread.

That's one of the things that makes measurement of this extremely tricky; the effects of school policies would be expected to appear slowly over time, and interact with the local conditions over that period of time.

Infectious diseases are super sneaky that way.

A better way of thinking about it is that a policy may change the trajectory of how COVID spreads through the population

The policy impact on even the intermediate changes (e.g. social interactions) takes hold over a few weeks in general

THEN that already widely distributed intermediary impact start subtly interacting with the trajectory of cases over time, also over the course of weeks.

The result is that even policies with HUGE overall impact are more like subtly shifted curves than cliffs.

Lack of either a spike or a cliff for school closings and openings really tells us very little, unfortunately, and trying to figure it all out requires a great deal of understanding of how policies might impact infectious disease outcomes.

Clear data signals are hard to come by.

Same is true for most other policies.

See, for example, the (often bad faith) argument that masks "don't work" because we didn't see COVID cases plummet after mask mandates started.

We also probably won't see cases immediately skyrocket in Texas for the same reason.