Not OP, but I think what was meant is identifying a vaccine that targets proteins(s) on the surface of the virus rather than only the little "spikes" that protrude from it. Early vaccine development latched onto the idea that the spike proteins are critical to the virus' ability to infect humans, so mutations would likely/hopefully/maybe make the virus less dangerous to humans anyway.

But, it would be ideal if we could also find proteins on the surface of virus that are less likely to mutate (than other proteins in the virus) that we could teach our immune systems to look for.