Even more consequential than the fact from the headline is the preliminary result that a spacing of 12 weeks does not seem to reduce efficiency. I wish my country and others would take note and give priority to handing out as many first doses as possible, but my hope for such quick adoption of scientific findings has been rather diminished by the whole event.
The first dose prevents hospitalization. Right now, for every second dose we give, that's a decision to deny someone a life-saving dose in favor of someone already protected. What a strange prioritization to make. The bright side is that, if the rate of vaccination continues to increase, those denied the first dose now should still get the first dose soon after. Let's hope we don't hit some manufacturing bottleneck.
Does 1 dose prevent the spread of COVID19?
If it requires 2-doses to get a true "efficacy" (lower spread), then it might be more worthwhile to push 2-doses, rather than 1-dose (where everyone gets "less sick", but the virus continues to spread exponentially).
Real problem: 1-dose wasn't really tested on a large "phase 3" style 10,000+ person test. Its impossible to answer this question (yet). It will take further testing to know.
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I think there's something to be respected about sticking with what was tested, even if the scientific theory argues for a different approach.
Just because the theory says so, doesn't mean that the theory is true (at least, not until the theory is well tested).
Doing something different and hoping for the best just because its kinda correct theoretically is... overly optimistic. I wouldn't necessarily be against it, but it makes sense to stick with what was formally tested.