I saw a YouTube video from a Doctor (he has several on COVID) where he was saying the Astra-Zeneca/Oxford vaccine would turn out to be the most effective. Because:
1) Old technology.
2) Claimed efficacy would probably improve with larger data, whereas the others may well fall due to distribution logistics with storage temperature needed.
3) $3/4 a shot means the take-up world wide will be greater. And it has to be a world solution, we are a flat earth (commercially speaking).

& I would add that the Serum Institute in India (the biggest make of vaccines) turned over all their production to the A-Z/O vaccine long ago. A gamble now paying off. India is a big market.

I see several of this parish have had the call to arm. Things is moving fast.