I know most people here like to defend the established ways of doing things. But in an crisis like this we need to go back to first principles and see which steps are really needed and what can be speed up.
a rushed vaccine that has poorly understood side effects like say cancer rate differences or is fatal for people with some other disease is more dangerous than the disease itself. Many more people will end up taking the vaccine than just those having the infection.
If this situation got really bad, what are the chances of this timeline being accelerated? The US has step 1 done now. Could we roll the dice on doing broader human trials immediately and also in parallel scale up production? Sure you might kill people in trials and waste lots of money, but may be better than the alternative of tens of millions dead.
My understanding is that it is very labor intensive and the manufacturing capacity is simply not there to make billions of doses in a short timescale (months).
2. Test vaccine on animals
3. Prove to regulators vaccine is safe enough for limited human trials
4. Conduct limited human trials
5. Research effectiveness of vaccine / absence of side effects
6. Conduct broader human trials
7. Step 5 again
8. Scale up production of vaccine
Now, imagine that you can fail at any step and go back to the starting point.