Resident, there is logic in your words, but part of the consideration is risk of exposure. The usual reason for extra testing of vaccines is that it is given to healthy population, of which only a small number will get exposed to a virus (think, Ebola or Yellow Fever).
In a case of a pandemic, when the pandemic is raging and those people who are at exposure (college, HS students in large groups, in poorly ventilated rooms, for example) might have say 30% chance of exposure or more. That is, you need to compare 1-to-1, or 1-to-3 risk/benefit from the virus v. risk from vaccine. Vaccine is developed by certified Western scientists, virus was developed by a team of bats and batmen. Vaccine is tested for extra safety, virus attacks your organs. Most of this is kal vahomer in favor of vaccine.
The only consideration might be an overdose. Vaccines had combined Phase 1/2 to test several doses, and then one shot to pass Phase 3 in time to save lives. I suspect that higher doses were used in order to pass the test for sure. Maybe, we should have had even more Phase 3s with different doses… Moderna just published that 1/2 and even 1/4 of doses seem to be effective, and this might be an approach to vaccinate more people in the world. “1/2 dose now is better than full does a year later”. Similarly, ongoing tests on children are using smaller doses. I see no reason why the smaller doses should not be used for any young person. There is also research showing that increasing gap between doses reduces side effects. I wish we could have voted to keep Pres Trump and his team to deal w/ Op Warp to sort all these issues out, while Pres Biden fights climate change and other sheidim.