While the news of high efficacy is thrilling and has exceeded expectations, several researchers have flagged some vital unknowns.
www.nationalgeographic.com
(Hopefully this does not get hit with a TOS violation.)
I have my pet personal conspiracy theory about the safety profile based on who actually gets the vaccine first. If the government keeps the first 20M or so for their own use and rich people like the PPE was hogged for them by FEMA earlier this year, then it's probably safe. If the government makes it a point to give it to IHS, 301b, etc., then I would think that the experts do not actually think the vaccine is safe, and the first RNA vaccine is going to have a lot of what Trump would consider to be worthless people as voluntary guinea pigs. Remember that this will be the first genetic vaccine (DNA or RNA) approved, so YMMV on the lifetime effects.
Recall though that there is already 20M doses right now at the ready through OWS funding, Pfizer and two of the other candidates are manufacturing ahead of the testing, there is major concern among us that the vaccine is in a too big to fail situation.
Somehow though, for as little the number of patients involved in the arguably Phase I study, that high a number is expected. Whether it works as it mutates is something else, but honestly, I'm going to let people who want it get what they want. I can afford to be cozy for another two years, it grows on you.
But my own pessimistic guess is that COVID-19 is just like every other coronavirus (SARS, HKU) where immunity is fleeting, and immunity to one strain is not immunity to next season's.