Thread by @gbrumfiel

A lot of people are tweeting about how this new Pfizer vaccine finding has not been peer-reviewed. That's true, but it's also important to understand that academic peer-review is not the only way to be scientifically rigorous... 🧵

In the case of clinical trials, there are a number of methods to keep bias out of data. One is to "blind" the trial, so that both patients and those administering the vaccine don't know who gets the drug and who gets the placebo. This trial was fully blinded.

In other words, patients, scientists, clinicians, and even Pfizer executives had no idea who got the vaccine and who didn't. Only a small team of statisticians and medical monitors remained unblinded to keep the trial on track. They had no direct contact with the trial team.

Additionally, this trial is overseen by a Data Monitoring Committee (DMC), a group of scientists and clinicians supposedly free of conflicts of interest and bias (though I think we're all biased towards a positive outcome of this vaccine trial).

My understanding is that the DMC and FDA determine when to "unblind" sections of the trial. Unblinding can happen before trial completion in part to learn of safety issues, or once enough trial participants have been infected to have SOME indication of whether its working.

But these unblindings happen only at pre-determined points. In this case, the decision was made to unblind after a minimum of 62 COVID-19 cases in trial participants. Presumably that minimum would give SOME indication of whether the vaccine was working.

In fact they unblinded at 94 participants infected. That's far short of the 164 needed to conclude the trial, but definitely enough to determine efficacy. And the conclusion is that the vaccine is more than 90% effective, a very high number/strong signal.

There's a lot still to learn including:

✅The actual efficacy (which could still be below 90%)

✅Whether protection is afforded across demographic groups.

✅The length the vaccine might work.

✅Whether the vaccine causes side-effects (though some safety work has been done).

But at this point I think it's reasonably to say this is more than science by press-release. There is every indication this vaccine is doing something to protect people against SARS-CoV-2. That's good news.

Now would peer-review be better still? Oh definitely. For sure. Hopefully we'll see it in the future. And hopefully we'll know more once the trial reaches 164 cases and is fully unblinded.

Also, this winter is still going to be bad. Wear a mask, keep distance. Take care.

Here are a few sources about the trial that I used for this thread.

Pfizer's announcement:
pfizer.com/news/press-rel…

The study protocol:
pfe-pfizercom-d8-prod.s3.amazonaws.com/2020-09/C45910…

FDA guidance on DMCs:
fda.gov/media/75398/do…

/FIN