On: Association between influenza vaccination and risk...

[dqv]

So the greatgrandparent can at best say they have never had symptomatic flu. They cannot confidently say they have never gotten the flu. It is flawed reasoning to use no symptoms of flu = not gotten the flu = not getting vaccine.

[t0bia_s → dqv]

This is not medical and vague argument.

Symptoms are what you "fight" against by medicine. Nonsymptimatic could be basically anything.