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Originally Posted by calculoso
All we know so far is that Pfizer has a better PR/Marketing department than the competition. Other companies could have a 91% effective rate but not want to say anything until later in their trials.... or be farther behind... or be worse... I for one just plain don’t know. I hope that people don’t put all the eggs in the blue pill company basket.
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It's not really a PR thing. All of these phase 3 studies have pre-set benchmarks at which point they unblind the data to get a readout to judge efficacy. Essentially they set several interim analyses at different levels of positive cases among their trial participants. Once they hit those benchmarks, they check to see which of the cases got the vaccine and which got the placebo. Pfizer just happened to hit that first, likely due to their early start and large sample size.
Pfizer initially set their first analysis at 32 infections, but the FDA rejected that for being too small so they negotiated to adjust it to 62 infections. However, while those negotiations were happening, the # of infections in the trial participants grew rapidly and they ended up with 94 cases (with nearly all of those occurring in the placebo arm). Moderna's first readout is at 53 infections and Oxford/AstraZeneca set their at 75 infections, so I wouldn't be surprised if we get readouts from those in the near future too.