So 1/3 of the subjects get a placebo? It was 50% in the Pfizer trials.
I assume that patients don't know what they're getting. But can't you tell from the side effects? If the placebo is just saline, the body is not going to react in the same way. There may be soreness in the arm just from having a needle go in, but there will be no immune response. Whereas, what I'm hearing anecdotally is that people who receive the actual vaccine have very noticeable other, systemic symptom, such as fever and weakness for 24 hours or so. So wouldn't you know right away if you got the vaccine?
Couldn't that knowledge affect your behavior? I'd think that people who know they have the actual vaccine, regardless of how they're cautioned, will be a little looser with social interactions, even if only unconsciously, than people who know they haven't received a vaccine. That could bias the results, making those who receive the vaccine more likely to get exposed to the virus, relative to the placebo, than would be the case if everyone was blind, and behaved more or less the same. IOW, the determined efficacy would be lower than it would actually be.
Seems to me that there are some other thorny problems here. Once the vaccine has been authorized, those who received a placebo are supposed to be notified, and in many cases, they had previously been promised, as a reward for entering the trial, that they could receive the vaccine if they had been a placebo. But many times companies want to extend the lengths of the trials, to get more data on adverse effects. In fact, six months is required for permanent authorization, as opposed to emergency use that has been granted so far. People who were placebos aren't going to want to remain in this situation, when they have a chance to get the real vaccine.
There is also the problem with vaccines that are still in trials, and haven't been approved. If a new vaccine is approved, is someone who is in a trial for an unapproved vaccine going to want to remain in that study, not knowing if s/he is a placebo, when a vaccine that definitely works may be available? What about new vaccines that haven't reached phase 3 yet? Who's going to want to volunteer, knowing they might be a placebo?
I'm over in the Phils, and now I hear that people my age may not get vaccinated, because of fears of bad reactions. The Pfizer-linked deaths in Norway also has the President here saying this confirms that Sinovac is better. My partner has some allergies, and supposedly people with that condition will also be barred from receiving the vaccine. What a mess.