So being that many great poskim lived between the mid 1800s and now and not one to my limited knowledge advocated closing all shuls in the winter or closed a shul based on this reasoning than your understanding is obviously wrong and the question is just why
That, or
Therefore, it is my understanding thus far that according to Halacha, we would indeed close all shuls every winter to save a single elderly flu victim, if not for the fact that we assume people will go out anyways, and so closing the shuls will no reduce the overall infection rate.
Seroprevalence accounts for all of those factors (except “innate immunity” which is a THEORY). If we were talking only of those people you described than mortality would be more than 5%..
+1.
This should be in a different thread, but I'm tired of arguments about the mortality rate. We have vast seroprevalence data from almost every town & country in Europe and many enclosed curiseships and aircraft carriers. We know the IFR with absolute certainty.
There is a very famous letter from R Akiva Eiger discussing limiting attendance to 15 people and actually having the secular police enforce it. There are MANY tshuvos among achronim discussing many different cases where they did not havea minyan for a few weeks due to various types of dangers and the like.
The year later RAE closed the Shul entirely, and that was before they knew the sickness was contagious. They assumed people were getting it by being exposed to the outdoors, dirtiness, and weakness.