It didn't. Western medicine new lead was poisonous dating back at least to the second century BCE. What changed was the belief that only acute lead exposure could cause poisoning... We came to understand the mechanisms by which chronic exposure causes buildup and poisoning over a long term.

This makes the analogy even more appropriate. We know the spike protein is harmful in some amount, but we think a small enough amount produced forever should be safe. Maybe we'll learn otherwise.

Why do you think it is produced forever? The mRNA quickly degrades in the body and the injected cells will stop producing the spike protein. That's why there has to be a second injection.

Is there a source? 100% believe you, but due to the conflicting posts I’d love to read the source (and I don’t know what to Google). Thanks!

(m)RNA is inherently unstable in our body: https://en.wikipedia.org/wiki/Messenger_RNA#Degradation

> small enough amount produced forever should be safe

does 'forever' modify 'produced' or 'should be safe'? if the former, what produces a small amount of the spike protein forever (continuing, not just a small amount one time)?