4 ms·

The phase 3 trials were already large: the Pfizer trial had over 40,000 enrolled patients. However, they were still optimizing for speed: they presented result

The phase 3 trials were already large: the Pfizer trial had over 40,000 enrolled patients. However, they were still optimizing for speed: they presented results to regulatory agencies as soon as they reached a threshold number of covid infections in the group, which allowed them to demonstrate efficacy. If instead they ran a split-dose trial, the results from each arm would have less statistical power, so the trial could not conclude until it sees more covid patients, taking longer overall.

jonahrd 6y ago
I think the idea is to run multiple trials, each _still_ with 40,000 patients. That way we could have approved a 2-week dosing schedule and started giving out the first doses, and by the time the first patients are ready for their 2-week dose, the results of the 4-week dosing schedule would be ready, etc, etc. So we could push back the 2nd dose "indefinitely", preventing this issue in the first place. (Assuming by the time the 2nd dose is really worth getting, we have already made enough vaccines that the scheduling details are less important)
- clankyclanker 6y ago
  You're neglecting the time it takes to recruit 40,000 patients. It's not fast or easy to identify those folks, as a significant number of people have disqualifiers (like comorbidities e.g., obesity). Once they're identified as candidates, you still need to go through the task of recruiting them, likely through their healthcare network. You can't just use automated calls for that because nobody's going to trust a recording that promises "Free Vaccine Fast, Act Now!" They likely ran the trial with 40,000 patients because that was all the qualified patients they were able to quickly contact reliably enough to include them in the study (otherwise you have study dropouts, as mentioned in other comments above).
- refurb 6y ago
  You can’t add more arms to a trial and keep the number tested the same without losing “statistical power”.

jonahrd 6y ago

I think the idea is to run multiple trials, each _still_ with 40,000 patients. That way we could have approved a 2-week dosing schedule and started giving out the first doses, and by the time the first patients are ready for their 2-week dose, the results of the 4-week dosing schedule would be ready, etc, etc. So we could push back the 2nd dose "indefinitely", preventing this issue in the first place. (Assuming by the time the 2nd dose is really worth getting, we have already made enough vaccines that the scheduling details are less important)

clankyclanker 6y ago
You're neglecting the time it takes to recruit 40,000 patients. It's not fast or easy to identify those folks, as a significant number of people have disqualifiers (like comorbidities e.g., obesity). Once they're identified as candidates, you still need to go through the task of recruiting them, likely through their healthcare network. You can't just use automated calls for that because nobody's going to trust a recording that promises "Free Vaccine Fast, Act Now!" They likely ran the trial with 40,000 patients because that was all the qualified patients they were able to quickly contact reliably enough to include them in the study (otherwise you have study dropouts, as mentioned in other comments above).
refurb 6y ago
You can’t add more arms to a trial and keep the number tested the same without losing “statistical power”.