That's an excellent question. So far the data appear to be encouraging. There doesn't seem to be an indication that if the second dose is delayed you will be more likely to need a third dose. It may very well be that we'll all need a third dose in the future.
That being said, really the point here that is most urgent is that health care workers need to be fully protected as soon as possible, because the incidence rates are high; they are providing frontline care to patients with COVID-19, and they do not have the option to refrain from direct contact with those patients.