Louis Gossett Jr
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Here’s a question I think I know the answer to, but would love an expert opinion.
If you were in a vaccine study, even if you have antibodies to the virus, that doesn’t necessarily mean you have a. Been vaccinated (could’ve been from exposure) or b. Received the recommended dosage volume, number or time in-between (might know this one). It’s not until you’ve been unblinded, that you’ll know for sure.
It might be that you received a smaller volume of the vaccine for dose 1 and saline for dose 2. You’d still have antibodies, but not reflect the 95% efficacy that people who get 2 doses of the recommended volume would.
The answer to your first question is it depends on the test being used. This was actually something I was working on a little while ago. The vaccine is specifically targeted to a region of the spike protein, a prime testing protein is to use a recombinant protein of the spike protein, so if you use an antibody test ELISA, Luminex, RDT lateral flow test that has single detection of spike protein then there is no ability to distinguish between vaccine and natural infection. However if you use a test with another antigen, such as the nucleocapsid protein or even better a test that uses both nucleocapsid and spike protein you would be able to tell. (Caveat for some reason in Africa populations there is a ton of non-specific cross-reactivity and you need 3+ targets for accurate serological testing). So say you had spike (Sp) and nucleocapsid (Nc) targets, the outcomes could be
1. No reaction to either = No exposure
2. Reaction to the Sp and not Nc = Vaccinated
3. Reaction to Nc and Sp = infected with the virus
Second question is depends on the phase of the trial, by Phase 2 and 3 you aren't usually deviating from the recommended forms. This was rushed so fast that things like dosing were kind of just best guessed from previous studies and animal studies (in the future i think we will learn that its way too high of a dose, especially in the younger healthy crowd, but it worked so went with it). Studies aren't controlled where two doses in compared to one dose require saline as a second dose. It would be first dose saline, first dose vaccine, then a different group first dose saline, first dose vaccine, second dose saline, second dose vaccine. Compare between groups and doses. Also once the efficacy numbers are reached, enough people in placebo group are sick then its free to be unblinded. While the vaccine group will be monitored and data collected for the next few years, knowing you have or don't have the vaccine no longer is important so all vaccine participants in the approved vaccines know now.