Scientists normally like to do experiments. You know, they like to mix this with that and see what happens. They like to take this thing and poke it and see how it reacts. In astronomy, we can't do that. The stars, the planets, the galaxies, are so far away that we just look at them, and we have to learn things by looking at them.
Now, when you get a viral infection, what normally happens is it takes days or weeks for your body to fight back at full strength, and that might be too late. When you're pre-immunized, what happens is you have forces in your body pre-trained to recognize and defeat specific foes. So that's really how vaccines work.
On every single picture on my Instagram page, you'll find a negative comment. My supporters will normally stand up to that hateful person, and then it will become a big argument, and it's just a lot. I try to tell myself not to listen to the haters, and I try not to read the comments because it's not worth it.