To be fair validating effectiveness of a medical intervention requires accounting for variety in people and making sure that it is safe across the board.

You don't need a pool of hundreds of thousands of the exact same particle and a control pool of the same or need them to roam about in the wild for months to ethically answer a question in physics.

If we were willing to immunize and deliberately expose a large pool of people the covid vaccines would have been finished with testing a lot faster.