“to what extent should public and private institutions be expected to accommodate people who, for no other reason than ignorance, choose to opt out of the collective responsibility to public health?”

Before we can answer that, we would have to define the risks.

For example, the polio vaccine has no logical basis for being mandatory in the US. The requirement of the polio in the US has no basis in science and it goes against the stated purpose of the recommendations as it does not weigh risks and benefits. Instead, it is an ideological stance. Polio has been eradicated from the US (except for cases caused by vaccines themselves) and most of the rest of the world. You could require it for travel to/from risky locations. We know that severe adverse affects vastly out number the cases of Polio in the US.