> eventually got COVID over a year (18 months?) since the original vaccine, so presumably it was offering no protection at that time

I think you've misunderstood how the vaccines work. The protection provided by vaccines is not 100%. It doesn't necessarily give you sterilising immunity. The immunity wanes, but still gives protection against severe outcomes for a long time. You likely got a less severe bout of covid because you were vaccinated.

> I was scared to get the booster

> I was so confident in the vaccines

How do you reconcile these statements?