In answer to the original question about 70% ....
There were 23,848 people involved in the trial with half getting a placebo.
131 got covid with symptoms
These 131 were split 101 unvaccinated control versus 30 vaccinated, so 70% less people got covid with symptoms than would be expected if it did nothing.
However there was effectively two trials because some got the wrong dose.
So overall it was 101 vs 30 - 70%
But wrong dose it was 30 vs 3 - 90%
Correct dose it was 71 vs 27 - 62%
The numbers of people taking part in the trial 23,848 is large and so the vaccine is very safe. The numbers getting infected were very small. They are large enough to see it does something very positive but I would not read too much into the efficacy rates. Just looking at the 30 vs 3, that could so easily been vs 2 or 4, based on how much someone coughed.
Edit: the other aspect is that within the control group there were the expected number of hospitalisations and fatalites. Within the vaccinated group nobody was severe enough to require hospital.