Well, they’re just taking the Microsoft approach now. The customers are the beta testers!
All vaccines must go through full phase 1, phase 2, and phase 3 trials in order to be approved for use in the United States. The 5 top candidates (as picked by the Trump administration) have all made it through phase 1 and phase 2 trials already. That means thousands of closely monitored volunteers have already taken a vaccine candidate as part of testing. Phase 3 trials are in progress now for some of the candidates.
Phase 3 means tens of thousands of volunteers take the vaccine and are monitored for both safety and efficacy.
President Trump cut through the FDA’s bureaucracy so the approvals didn’t sit on some FDA employee’s desk for 6 months. No corners have been cut in safety or efficacy testing. It would not be legal to do so. Also, phase 3 testing is ongoing in other parts of the world as well. The UK has multiple candidates in their own phase 3 trials.
Any vaccine offered to the general public has been tested with tens of thousands of people over the course of several months.