Then and now, if you are in the military, they can make you take just about anything they want you to - risk v. benefit. High risk for death for the majority of people, that’s one thing. Very low risk for death for the majority, that’s another story. Death from flu is usually due to complications that lead to pneumonia. If you have a high-risk patient, everyone should put a mask on regardless of whether they had a flu shot. A simple cold can take such patients down.
“Death from flu is usually due to complications that lead to pneumonia. “
That may well be the case for most human flu strains.
The big trouble comes when a hybrid human/animal flu gets going. The level of worry spikes when you start seeing evidence of swine flu or avian flu crossing with human flu.
The normal human flu kills the weak and infirm. The hybrid strains kill the young and strong, adults in their prime. The hybrid flu will provoke a massive immune response in the lungs, a cytokine storm, and you literally drown in your own antibodies.
The 1918 influenza was such a hybrid flu and it was extremely virulent. Children were known to have kissed their parents goodbye as they went to school, and when they returned home learned that they were orphans. It would kill that quickly. My own grandfather contracted it on an Army post and it nearly killed him. There were so many cases that it overwhelmed the medical staff and they brought in civilian volunteers to nurse the sick soldiers.