system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what are chickenpox and why does everyone get it and only once?

doesn't it seem strange that we just accept this virus(or whatever it is) just being passed around ?
gpt
It's a virus, and typically with viruses, you only get it once. Then your body has made antibodies for it so it can fight off the virus if you're exposed again. However, your body doesn't completely cure you of the virus. The virus stays dormant in your nerve tissues. Then, years later, it can resurface, but instead of taking the form of chicken pox again, it is shingles, which are itchy, painful sores that inflame your nerve pathways. It's very unpleasant. 

It was kind of accepted as just happening because it's not usually that dangerous as long as you get it as a child. When adults get it, it can be a lot more dangerous and there are deaths every year from it. Shingles can also be quite a plague on people. So they have developed a vaccine for chickenpox and a vaccine for shingles. Neither vaccine lasts that long so you have to get it several times.