Your response is phrased in a way that all the meaning lies in the exact definition of what you mean by "knows". There is certainly evidence that there are long-term effects. Example: https://www.medrxiv.org/content/10.1101/2020.10.20.20215863v...

This huge uncertainty is in favor of avoiding taking the risks, rather than the other way.

Put another way: Nobody knows of any long term effect on the body.