What happened to our immune systems?

I remember learning about the immune system in college. I remember my professor saying that in order to get sick with something you had to be a susceptible host. Your immune system would have to be compromised or immature in order get sick. Fast forward about twenty years and now we are told we have to take a pharmaceutical product, or have to mask, or have to isolate yourself in order for you to stay safe and not get sick. This is a contradiction to everything that I was taught. Our bodies when functioning properly are designed to fight off foreign invaders. How did we make it this far without this dependency on modern medicine? We are designed with immune cells that specifically target and attack things that it doesn’t recognize. I’m sure you have noticed when you are run down or stressed out your immune system plummets. You get sicker easier. I think the most important thing that people can do right now is to protect their health. There are many simple things that you can do to boost your immune system such as getting adequate sunlight, good nutrition, hydration, getting good sleep, and managing your stress.