Perhaps I am making an incorrect assumption, but when it is reported that 30,000 participants are being inoculated, I take that to mean that about 15,000 are getting the vaccine and about 15,000 are getting a placebo. But then I see this:

Statisticians have been crunching the numbers to predict how many infections would need to occur in the study population to gauge the vaccine’s effectiveness. To show the Moderna vaccine is 60 percent effective, Fauci said, there would need to be about 150 infections among the 30,000 participants. WAPO

That leads me to believe that the number of persons being innoculated with the 'real deal' is 30K, meaning that the entire pool, including the control group, is more on the order of 60,000.

Are there 30K volunteers or 60K volunteers?

  • 1
    I don't really follow your logic. Fauci's statement doesn't have any relevance to the placebo vs test group; you suddenly infer this must relate to the test group. Fauci seems to be giving just a broad brush statistical objective. Please don't read extra stuff in that he hasn't said.
    – Bryan Krause
    Jul 29, 2020 at 3:58
  • 1
    @BryanKrause The logic relative to Fauci statement is not essential to the question of who many persons will be inoculated with the trial vaccine. OTOH, IF there are 30,000 participants (as Fauci said) and IF the 150 who contract the disease ALL are in the control group that would suggest an effectiveness substantially in excess of 60%. That said, it should not distract from the question of how many are going to actually receive the trial vaccine.
    – BobE
    Jul 29, 2020 at 14:26
  • @BryanKrause - but since you mention it.... is 60% the objective ?
    – BobE
    Jul 29, 2020 at 14:28

1 Answer 1


The article makes it clear there are a total of 30K participants with 15K receiving placebo:

The vaccination marks a much-anticipated milestone: the official launch of the first in a series of large U.S. clinical trials that will each test experimental vaccines in 30,000 participants, half receiving the shot and half receiving a placebo.

How Fauci comes up with 150 infections to demonstrate a 60% effectiveness, I do not know, but I would expect he knows the details of the statistical analysis being used and what their assumptions are about the odds of becoming infected.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.