It's a good point. But delivery mechanism should probably be considered too. The virus has to go through the respiratory system, which is a first line of defense. Then it takes time to infect you, multiply, and get around. It also can only dock at ACE2 I think. The shot seems to be instant full body intracellular delivery.

Maybe it does not matter much, but the immune reaction can indeed be very strong. Just don't be completely naive when in comes to regular booster shots, there might be a fine line between benefits and negatives. Also other types of vaccines are on the way I heard, so we'll see, maybe that will open up alternative ways to combat the virus.