We are entering a new phase of humanity’s COVID fight.
It might be a profoundly hopeful one; or it could be supremely dangerous.
With vaccination programmes starting to ramp up quite rapidly, at least in the developed world, we could be only a few weeks away from a situation in which mortality rates are in sharp decline and a high proportion of the most vulnerable have a degree of immunity.
In much of the developing world, things will take longer.
There was no disguising the urgency of World Health Organization head Tedros Adhanom Ghebreyesus' recent warning that the world faces a "catastrophic moral failure" over vaccination policies.
It is hard to blame national politicians in wealthy countries for prioritising the protection of their citizens in crisis situations such as the one that has engulfed us for the past year - especially in times when overt nationalism is such a vote-winner.
But, of course, the interests of the relatively rich lie in conferring a good degree of immunity on poor countries every bit as quickly, or almost, as their own societies.
Organisms mutate, or evolve.
If a COVID-19 strain emerges that is resistant to our new vaccine batteries, it matters little, except perhaps in the very short term, whether it originates in Birmingham or Burkina Faso.
Yes, vaccines can - and, one would hope, would - be tweaked.
But, at least for a period, we would risk being catapulted back to square one - and with everyone’s fuse being a little shorter than when we first faced up to this cruel impostor a year ago.
The coming months may, therefore, see the world plunged into a period of see-sawing emotions, in which victory over the microbe appears, one minute, to be at hand, only for some new obstacle to materialise from some hitherto unsuspected direction.
This would be in sharp contrast to the relatively uniform gloom that enveloped us last year, until that initial positive vaccine trial triggered the first, hugely relieved if somewhat premature, emotional convulsion.
What does this new state of play imply for the International Olympic Committee (IOC) and its Tokyo 2020 conundrum?
Well, if they were very lucky, it is still just about possible to imagine those declining mortality trends emerging in time, and remaining for long enough, to render the current July 23 start-date viable.
But there seems little scope to absorb any further setback, especially with large-scale vaccinations not expected to start in Japan itself until March.
And, even in the best of circumstances, including the assumption that Japanese public opinion might be coaxed back in favour of the Games, it still appears to me highly likely that representation from poorer countries would end up being severely truncated, with athletes and the IOC carpeted, rightly or wrongly, for barging into the vaccine queue.
One thing the IOC does not need is for its light at the end of the tunnel to turn out to be the stroboscopic glow of a rich kids' party.
July 23, in other words, is looking like a bigger and bigger ask with almost each day that passes - and even if they ultimately got away with it, Olympic leaders would be condemning themselves to a nerve-shredding white-knuckle ride of six months’ duration.
But - and it is an important "but" - it is possible to believe all the above while also thinking that by August, September, October, the coast might be relatively clear.
There is no guarantee of this, but it might.
It would be a shame in such circumstances to knock the Tokyo 2020 event on the head once and for all the moment it became generally accepted that a July 23 opening was a no-no.
No-one can say exactly when - and there remains all sorts of scope for any prediction very quickly to acquire a lustre of stupidity - but the prospects look relatively good that at some point between, say, September and November 2021, conditions might be favourable enough for most reasonable-minded people to accept that an Olympic Games would come as a welcome and acceptably low-risk morale-booster.
That could also be true of the winter months; but the planned February time-slot for Beijing 2022, not to mention the weather, rules out the December 2021 to March 2022 period.
April 2022 could yet be the real last-chance saloon for a Tokyo Games.
I am not sure that slippage into the summer of 2022 is any longer feasible. Aquatics and athletics World Championships are now scheduled respectively for May and July of that year, and it would seem pointless salvaging Olympic TV dollars only at cost of World Championship TV dollars for the Games' two biggest sports.
So, whatever they say in public, it seems to me there is a case for Tokyo 2020 organisers to move away from any fixation with set-in-stone dates towards a focus on event delivery systems.
These should be knocked into good enough shape to make it possible to deliver, well, some sort of Summer Olympic spectacular with as short an interval as possible between that moment, if it comes, when our vaccine programmes have demonstrably got the upper hand, setting in chain a virtuous spiral, and the Opening Ceremony.
Then, and only then, would organisers have the luxury of a certain amount of relatively low-risk time, since, even if victory over the virus proved not to be definitive, there would be an interval before any pernicious new trend reasserted itself.
Ideally, I think organisers should aim for an interval of two months between giving the green light to proceed on a particular date and igniting the Cauldron.
Obviously, such a time-frame would entrain its own problems; one could foresee a cacophony of protest from stakeholders, be they athletes, corporate sponsors, broadcasters or, perhaps most seriously, security services.
I very much doubt under such circumstances that Mohamed Salah would spearhead the attack of the Egypt men’s Olympic football team.
But I think we are now beyond the point where a "normal" Olympics can be expected.
The choice is between "something" and "nothing".
And, if by adopting that approach, the IOC maximised the prospect of salvaging at least a portion of the $3 billion (£2.2 billion/€2.5 billion) of TV money - my estimate - that might be lost to sport in the event of out-and-out cancellation, then it could come to be accepted by most interest-groups as the least-bad option.
It doesn’t sound very good in Latin: "Citius, Altius, Fortius, Ille Pedum Melior".
Nevertheless, "Faster, Higher, Stronger, Nimbler" might be an appropriate mantra for organisers if Tokyo 2020 is to be saved.