This is why the Spanish flu, the Swine flu, and H5N1 are most devastating to relatively young, relatively healthy individuals (their immune systems are the strongest).
The truth is that the complete opposite of what you claim there is what occurred. H1N1 (which I could easily find the numbers for) was most devastating to those with weaker immune systems, as most people would expect.
Age group--specific H1N1-related death rates were 3.5 for persons aged 0--4 years, 1.1 for persons aged 5--24 years, 4.2 for persons aged 25--64 years, and 7.2 for persons aged ≥65 years.[1]