Median age of Italy is like 48yrs, which is 10yrs older than US. It might be the oldest population in the World (you will have to check me on that). You are still correct that the oldest are most vulnerable, but we knew that. You solution would be fine except those in the higher age brackets are not the only ones vulnerable. So for the 40yr old that gets it and dies do we just call it collateral damage? In the end, solutions for a democracy are different than solutions under an autocracy.
I'm not saying it is right, but that is what we have been doing for the flu for hundreds of years. 20,000 to 80,000 in the US die annually from the flu. I have seen a handful of schools shut down for less than a week to do extra cleaning because of a bad flu outbreak. But that is as severe as I've seen.
I can't ever remember one major event that was shut down for the flu. Heck Michael Jordan had probably his most famous game in the "flu game" in game 5 of the '97 finals. Nobody blinked an eye and he was praised for getting out there and battling with the flu. What about all those people that die every year?