I have had, approximately, 15 flu shots in my life. Sure, you say, the flu changes constantly. I think I've had something like 7 or 8 Tdap shots. The vaccine

I have had, approximately, 15 flu shots in my life. Sure, you say, the flu changes constantly. I think I've had something like 7 or 8 Tdap shots. The vaccine schedule on that is 3 shots two months apart, another shot a year later, then 2-3 years later, then every ~ten years after that. Why is "You need more than one shot" such a silver bullet argument?