I appreciate this response, and agree with much of it.

There's some grey-area stuff:

Evolution is messy, and the evolution of the immune system is messier still. Even if we only look at it from a simplified Darwinian evolution perspective, having genetic diversity might be more important than any shedding of 'weaker' alleles from people dying off because their natural immunity couldn't handle a particular infection.

True, but in theory, a good chunk of people would be taking vaccines - and so while there's a selective pressure (mostly on those willing to undergo it), overall diversity would be maintained.

and, as an aside -- alas, simplified is the domain and utility of science. It's how we grasp anything natural at all.

..there are some tidbits I do disagree with, though. mainly:

Someone's HLA alleles can be a poor match for a current disease, but very helpful for a future disease. Having them die off now would be a bad thing.

While that would be a bad thing, it's not like there's selective pressure against having the HLA alleles that would be good for a future disease - more, just that there's selective pressure against not having one for the current disease. Let's say that the theoretical future-disease-preventing HLA alleles are randomly distributed, and that the incidence of death from a current disease roughly matches the incidence of death from car accidents, then the car accidents have just as much of a deleterious affect on the future as the current disease does. That's like the Christian argument "The baby you're about to abort could be the one that comes up with the cure for cancer." ..sure, but it could by Hitler 3.0, too.

The very multifaceted complexity that goes into the entire process of how animals (including us) handle disease has a couple knowable facets:

• It works, generally speaking, over the long term, and often enough in the short term

• we have added new means of gaining immunity, but with that we also reduce selective pressures on the species, not just for disease-specific immune responses, but any other traits (including but not limited to rapidity of immune response) that impact the capacity to handle and survive a disease

• it is clearly selection pressure that has led to effective immune systems in the first place

but even aside from that, the following are my opinions, and though I'm open to the possibility, I doubt they'll change today:

• taking away the body sovereignty of an individual is an abominable act which reduces diversity, and harms the species as a whole, in many different ways, some subtle, some less so
• the benefits of body sovereignty far outweigh the detriments of it, particularly since we, by and large, have a medical answer for those who wish to be protected from a disease but don't want to rely on the natural biological process to do so, but would rather use a method that involves a technological support framework.
• evolution works, and although it always costs lives, it's a prerequisite for life. We don't evolve out of evolution.

edit: btw, thanks for the genuine civil discourse, I enjoy it.