that's not pessimistic. Regularly only 6% of vaccines make it past trials.

Yes, but with each trial stage a particular vaccine candidate passes, its likelihood of failing the further stages goes down. Most candidates that are going to fail, do so in the lab or in Phase 1 trials. A vaccine candidate that passes Phase 1 and Phase 2 has a pretty good outlook.

Do you have a source, because I provided one, and if you look, it says:

"Approval rates ranged from a high of 33.4 percent in vaccines for infectious diseases to 3.4 percent for investigational cancer treatments"

So by that source, I was wildly pessimistic.

Above I asked for a source for the 6% number. I randomly came across a second-hand source in this article that actually used that same number:

https://www.thelancet.com/journals/lancet/article/PIIS0140-6...