It's about the number of patients, not the time. It's cheaper to run a trial over a longer period of time, a few patients at a time, but they don't continue to track patients for the entire duration. In this case tons of money was thrown at it and they were able to run tons of patients in parallel. Billions of doses of the vaccine have been given - seriously, what more do you want?
Because mRNA vaccines doesn't contain the dangerous virus at all, "just some genetic information" which will trigger your immune system to build antibodies. Things move forward, TTM for software features these days are often shorter because of technical advances, why wouldn't the same be true in biotech?
