From what I've gathered, it's more like: It's likely that the vaccine will have reduced efficacy (seen over the whole population) against this new strain. That'

From what I've gathered, it's more like: It's likely that the vaccine will have reduced efficacy (seen over the whole population) against this new strain. That's because your immune system essentially learns to recognize a random part of the virus, and if it ends up "training" itself using that part of the spike protein that's changed in this strain, it won't detect the virus.