Hello, thank you for your question!
Indeed, younger people are more likely to "grow out of" a COVID infection. However, this percentage is unfortunately not zero, and younger people are also at risk of developing quite severe symptoms that are now known as long term COVID.
The long-term effects of the vaccine are well known, but an infection with Covid are much more difficult to predict.
Furthermore, the vaccine could not only protect you, but your family members and friends as well, which is not to be overlooked
Finally, I just want to clarify your statement that "correlations exist between mRNA vaccines and autoimmune diseases", which is completely false.
This type of vaccine does not activate or worsen an autoimmune condition, nor does it trigger new ones. The warning is for people who are taking medications that could potentially weaken the immune system, which may decrease the immune response (and effectiveness) of the vaccine, but not make their condition worse.
This is why we rely on experts in immunology, chemistry and biology and not the average person on the internet.
I hope I've been helpful, I'm still available if you have any other questions!
Tom Samaha, pharmacist