If the vaccination effort is more piecemeal-as it is in the U.S. now with the plodding rollout-there may be more opportunities for SARS-CoV-2 to develop mutations that make it resistant to the vaccines.
He made no reply to this adjuration; only plodding doggedly down the wooden steps, and halting before an apartment which, from that halt and the superior quality of its furniture, I conjectured to be the best one.