4 ms·
They took essentially the approach most likely to be effective and deliver results as fast as possible. If you choose the overly conservative choice on dosage y
by Exmoor 6y ago
They took essentially the approach most likely to be effective and deliver results as fast as possible. If you choose the overly conservative choice on dosage you might possibly end up with not meeting your efficacy goals and end up either having to rerun phase III.
The duration between doses was chosen because it was the minimum plausible time that the second dose was likely to provide significant additional benefit, and therefore the fastest to test. It's entirely plausible given what we know about other vaccines, that delaying the second dose 8-12 weeks may actually have been more effective long-term, but if they'd done that the end of the testing (and therefore approval) would have been delayed another 4-8 weeks.
- myself248 6y agoIt's strange to me that they couldn't test several dosing regimens in parallel. Surely this would present no more moral dilemma than having a control group in the first place. It's just a question of numbers and resources, and if there's ever been a vaccine trial in history that could afford to throw numbers and resources at the problem, this is it. Was there some legal or regulatory reason not to do this obvious thing?
- pkaye 6y agoJ&J is testing both a single and two dose regime so its possible.
- Majromax 6y agoThe 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 agoI 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 agoYou'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 agoYou can’t add more arms to a trial and keep the number tested the same without losing “statistical power”.