DY, I agree that this consideration might not fully apply to the vaccine.
Argument for bracha – prison/desert are not direct danger, they are just a place where you are very likely to get hurt. So, this is same as unvaccinated person during pandemic.
The way I thought bracha does not apply – a non-careful person’s danger is primarily due to his own actions. But, the danger would still exist for most reasonably behaving people and sources I quoted are ambiguous, so I’ll concede here.
Another interesting aspect raised by Minchas Elazar – we are supposed not to quote Torah in the name of those who are not careful. Anyone can help me understand Minchas Elazar and the sources? B Kama 61b seems to be referring only not to encouraging self-sacrificing, not fully disregarding such a scholar.