Given that some vaccinated people still die, a booster shot now and then seems like a much safer strategy.
Bad analogy. What happens is that we're shooting people with .22LR (spike protein inducing mRNA) hoping it will help building immunity to bigger calibers (Covid19, not even talking about the variants).
It was bad on purpose. You can't compare the immune system to guns (like the parent does) or the Covid vaccine to seatbelts.