As we age, our immune response capability becomes reduced. It's why the average covid death is 82. Having a healthy lifestyle boosts your immune system--fruits, vegetables, less stress, sleep, weight control, exercise, less alcohol, etc. The reason most people get colds or flu in the winter is we stay indoors more (hello shelter in place bullshit).
The meme makes a point. The immune system is adaptive. You can't hide from germs. Coming in contact with germs triggers your immune system and a record is stored for future fights. Your body creates new antibodies whenever it’s infected with a new antigen. If the same antigen infects you a second time, your body can quickly make copies of the corresponding antibody to destroy it.
Look at the data. Italy and the UK are showing 95% of covid deaths are elderly or preexisting conditions (at-risk immune systems). My guess the other 5% are immune related issues (alcohol, fatigue, stress, poor diet, overweight, etc). In time we will look back and realize this was panic porn pushed by the media and ill informed leaders. We will shake our heads and wonder how dumb society was in 2020.