Escalating Failure

No, I'll stand my ground

Won't be turned around

And I'll keep this world from dragging me down

Gonna stand my ground

And I won't back down
--Tom Petty

Although the pandemic has been rich with examples of 'escalation theory,' where people continue or increase commitment to failing courses of action, there may not be a better one than those sticking with vaccines despite their increasing failure rates (and risks).

Escalation theory can be joined with prospect theory to explain why people who have been vaxxed multiple times cling to the idea of getting vaccinated despite breakthrough infections. Because people hate losses, including loss of self-esteem when a strongly held belief appear to be wrong, they will cling to those beliefs and perhaps even double down (e.g., my infection would surely be worse if I wasn't vaccinated) rather than question their assumptions.

Add some psychological concepts from what we know about cognitive dissonance, and you've built a solid theoretical foundation for explaining the odd behavior that we're witnessing.