Well, if trading is "thin" on Wednesday, Friday's trading will be "emaciated". Friday is out, imo, because the boom will fall on very, very few ears.
The only thing pulling me toward Wednesday pre-open is that announcement can also be a "filing for EUA" announcement since 11/25 is two months following 15,454 shot twice as of 9/25. They probably don't have to wait until 11/25 to have "more than half" two months after second shot. Even if they had 30,000 enroll, the most who got second shots is 28,422. This assumes no dropouts on the 2,768 who enrolled between 9/25 (27,232 of whom 25,654 got second shots on time) and 30,000. So half of max second shots = 14,211. Nevertheless, they may want 15,000 for show because it's half of 30K and they have that a day or two or three before 11/25.
I would not rule out today after the close as I think that would have as much bang as tomorrow, whether pre or after. My guess is here because I think they have the safety data and I cannot believe they have not accumulated 56 cases since 11/11 with infection rates raging as they are. Maybe they just have a lazy independent monitoring committee who does not work on weekends.