I've had the flu countless times and never have had a flu shot. I've also had the common cold countless timesBeing it was not tried in the opposite way of remaining open and working. There is nothing saying that it would be completely behind us right now. Can only speculate.
The flu too yes like Corona can lead into pneumonia which can but not always leave you with lung damage. And yes if severe you will need to be placed on ventilator.
And im willing to bet if and when they come out with this vaccine. It will be similar in results as the flu shot. Hit or miss.
Not once did I ever end up on a ventilator or with pneumonia.