If you think that our bodies protect us against most bugs that are doing the rounds otherwise we would be continually ill. So most people in the 1st World have a good immune system. Why does a human 'catch' anything? If the bug could be irradicated as polio/smallpox has been in the UK then there might be a firm reason to give an apparently healthy populas innoculations .............
I do remember well how ill I felt when I had the 'flu - 2 years running in March of those years, early 1980s. I was too ill even to contemplate ringing the GP
- I told DH that "I'm not hot or anything" but the flannel with which he was sponging me down was steaming
then he carried me to the bathroom which faces East and oh so bright
.............. Went to bed both times feeling fine, no warning; woke with aches, painful backs of eyes, not wanting to move .......... took about 3 days each time before I dared to lift head from pillow