Lots of interesting hypotheses on this thread and lots to respond to. Here's one item I haven't seen discussed yet.
There is a lot of discussion about how quickly Japan should be able to vaccinate enough people- volunteers, health care workers, vulnerable population in time for the Games But in reality, all of these people must get their first dose of Pfizer/Moderna vaccination within the next two weeks to be ready for Opening Ceremonies. I have not seen any plan showing how this can be done.
Here is the timeline in reverse order:
July 23: Opening ceremonies
July 16: 1 week build-in period for travel, volunteer training, etc. This is a reasonable estimate for target date of full immunity for target populations: athletes, training staff, coaches, volunteers, vulnerable population, etc.
July 2: Max immunity is cited as 2 weeks after 2nd dose of Pfizer/Moderna. Therefore, second dose must be given by this date.
June 11: 3 weeks before the 2nd dose. In the case Moderna, its 4 weeks, but we'll stay with the shorter period for now. So June 11 is the date for initial Pfizer dose
May 28: Today
The 1 dose J&J vaccine could accelerate this, but J&J only filed for approval in Japan on May 24, and says it won't roll out its vaccine there until early 2022. It is not widely available in all countries so I didn't include it above.
You could argue with the 1 week advance time before the Opening Ceremonies- which is balanced by my selection of 3 weeks between doses (Pfizer) vs. 4 required by Moderna.
So- the bottom line is that in order to argue for vaccinations as a solution, there are 14 days left to figure out how.