system
Given the following post, respond as if you're commenting on Reddit:
human
Why do young, healthy people have more intense vaccine reactogenicity but get less sick when they catch a virus?

I've read that young, healthy people are more likely to experience side effects from the COVID vaccines because of a robust immune response. So why do young, healthy people experience fewer symptoms/less intense illness when exposed to an actual virus?
gpt
Because young healthy people have stronger immune systems. The “vaccine reactions” are not directly due to the vaccine (this is true of all vaccines) but symptoms caused by the immune system “turning on” in response to the vaccine and develop that future protection. For the same reason, a young healthy person with a strong immune system will generally be able fight off the virus faster/stronger so won’t get as sick.