It doesn't matter as long as the sample size is large enough and randomized. The people who do these tests apply sound statistical procedures during the experimental design and interpretation of the results. The assumption is that the exposure is the same, in an average sense, for the two groups. The efficacy is the ratio between the positive cases of the two groups as tested some period of time after the second dose. Since they are dealing with relatively small numbers, about 170 positive cases out of about 40,000 total participants for the Pfizer/BioNTech study, the application of sound statistical procedures is important.
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Originally Posted by coffeebean
I have one question as to how the Covid vaccine efficacy is determined. From what I understand, people who participate in the vaccine trials are either vaccinated with the actual vaccine or are vaccinated with a placebo. Then, all of people who participate in the trial go out into the community to "live their lives normally".
Now the question.......are those people in the trial wearing masks and social distancing or are these people in the trials not wearing masks and social distancing? Even if the trial people do follow guidelines, people around them in the community may be following guidelines and wearing masks and social distancing.
I hope you are following my train of thoughts here. Bottom line......just how is the efficacy of a vaccine determined if masking and social distancing are being practiced by those involved in the trial and by the community they are exposed to?
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