[moistrobot]

if it's the same shot as the originals, which is my understanding, then it's reasonable to assume a similar expiry

[arrrg]

No, not at all. That’s not at all how it works.

Other vaccinations are also given three times (second dose after a short interval, third dose after a longer interval), so it might well be that this vaccine turns out to be one of those, we just do not know. That’s the point.