… We don’t see what we don’t look for.
A closely related issue is that of confirmation bias. We notice facts that support our worldview, and are blind to those that may shake our beliefs. It’s the way human brains are built. (Jonathan Haidt explains this wonderfully in videos, and in his books).
This is why I was concerned when our mass COVID vaccination campaign started. The vaccines were new technology, never before used on a large scale. Plus, we were vaccinating in the middle of a pandemic for the first time ever, which raised concerns that we might cause antigenic imprinting, or potentially select for vaccine-resistant variants in the same way that antibiotic use can drive the evolution of super-bugs.