the traditional safety and efficacy trials. and the bet was that if they proved successful, we will have already accumulated tens of millions of shots, and it worked. it's a messenger rna vaccine. and that basically means it's a blueprint of a part of the virus. you put that blueprint in the body, and the body in and of itself sort of acts like a vaccine factory. it didn't come out of nowhere. it came out of 20 years of previous research on trying to make mrna an effective therapy. here comes covid, and suddenly we need it fast. [tom] pfizer executives are calling it one of the biggest medical breakthroughs in the past 100 years. a covid vaccine developed in just six months. 90% effective in the group of drug trial volunteers who were known to be infected. i almost broke into tears because that was so unbelievably high for a vaccine to be that effective on the first shot. [dr. emanuel] it is remarkable, and it shows you what can happen