[RealFloridaMan]

The point of a vaccine is to not get the actual virus, or at least to minimize its effects if infected.

When you are infected with anything, you do not always develop anti-bodies. If you do develop anti-bodies, they might not be effective at actually stopping you from being re-infected.

Everything about the virus can mutate, but the virus will always target the ACE2 binding site. The spike protein can mutate to bind to it differently, but it will always require a spike protein. (Biology is Analog, not digital)

Thus targeting the spike protein is more efficient as it will be highly conserved.

There is a video series that does a nice job of breaking down how your immune response works: https://youtu.be/lXfEK8G8CUI

The vaccine is more effective at developing anti-bodies for the spike protein as it is the only protein exposed during the process.

An analogy that has helped some of my family: The virus is like a missile, and your immune system is a anti-missile system. Regardless of what the missile looks like, it has to have a warhead, and that warhead is what really defines what the entire thing does. So, if your defense systems targets the fuel of the missile, the enemy can change what fuel it runs on and evade your defense system. They can change the material it is made of, the shape of the overall device, change the propulsion and navigation systems…but the warhead can only have minor changes as it has because it it makes too many, it becomes ineffective and is no longer a threat.

Thus, if your defense system targets the warhead none of the other changes matter.