Could I lock myself out of getting immunity?
November 14, 2020 9:50 AM   Subscribe

If someone participates in a clinical trial for a vaccine, does that preclude that person from also receiving another more effective vaccine later, or make it risky to do so?

Mrs. Lips and I have an opportunity to participate in a Phase 3 clinical trial for a Covid vaccine candidate we'll call 'A'. Let's assume that we receive the vaccine vs. a placebo, and while it gets approved / distributed the efficacy is significantly less than vaccine candidate 'B' which also goes to distribution.

1) Would we ever know if we received the vaccine vs. a placebo after the conclusion of the trial?

2) How likely is it that this would somehow preclude us from opting to also receive vaccine B later if we felt it was more likely to protect us? I know there's no good answer specific to Covid yet, but in general, do similar vaccines work together (kind of an additive effect) or do they compete against each other, reducing the efficacy of both? For purposes of this question assume A is vector-based and B is mRNA, if that makes a difference.

3) If several current candidates are eventually approved and go to market, how likely would it be that the public is recommended to receive multiple vaccines from differing sources? Who chooses which one(s) we should get?
posted by SquidLips to Health & Fitness (5 answers total) 6 users marked this as a favorite
 
Oh I just asked a friend who signed up for a vaccine trial some of these very questions yesterday! It probably depends on the trial, but for the one she did, you are allowed to get vaccine B if it comes out in general distribution before the trial is over, as long as you tell the people running it. (I know that doesn't answer your question about whether they interfere with each other, which I don't know the answer to.) And you can ask at the end of the study period whether you got placebo or not. But also these are very reasonable questions to ask the people performing the study and you should ask them!
posted by babelfish at 10:58 AM on November 14, 2020


Best answer: I am an immunologist, but I am not your immunologist, and I am definitely not a clinician.

1. The person who does the intake for your trial should be able to answer this question. You can ask it before agreeing to enroll.

2. I am not aware of any past situation, where getting one vaccine precludes getting a better vaccine later. In fact, I can think of several situations where folks who got a first-generation vaccine were later encourage to get a new-and-improved version (Polio and Shingles.) We won't know by the time you would want to be getting vaccine B how the vaccines would interact. Basically all the vaccine candidates are against spike at this point though, so I'd expect that they would be able to boost each other at least somewhat, even if not optimally. The most likely way I can imagine them competing, is if they were both vector-based, and they used the same vector (likely Ad5.) In that case, you might already have antibodies to the vector that would prevent it from infecting your cells again, so your immune system would never "see" the relevant antigens in vaccine B.

3. The public will not be recommended to get 2 different vaccines. Nobody will have tested it at the point when these start getting rolled out. It is going to be a logistical nightmare just to make sure people get boosted with the same one they were first vaccinated with. Notably, the J&J candidate only requires one dose, which lowers the complexity of getting everyone vaccinated significantly. Who chooses which you will get? You will get whichever one your doctor's office or local health department or whatever has available. Even with everyone working like mad to get many millions of doses made as fast as possible, there is not going to enough to go around for quite a while. If you have access to vaccination, you're going to have to take-or-leave the one that's available to you at that time.

Oh, and thanks for considering volunteering for the trial! None of this can get done without folks like you!
posted by juliapangolin at 11:00 AM on November 14, 2020 [15 favorites]


To add to the answer to the last part of your question, vaccine recommendations for the US are made by the CDC’s Advisory Committee on Immunization Practices (ACIP). These are the people who would say, for each FDA-licensed vaccine, what kind of people are recommended to receive it (e.g., age range, pregnant or not, health contraindications and precautions), how many doses, and how long between doses. The American Medical Association, American Academy of Pediatrics, and other professional groups have liaisons to this committee. So this will be part of the determination of who should get which vaccine, but if, as seems likely, multiple vaccines are licensed, you should be equally well off, as far as the state of the science today is able to tell us, getting any of the vaccines whose recommendations apply to you.
posted by lakeroon at 1:35 PM on November 14, 2020


Former clinical research coordinator here. Look in all the fine print of the Informed Consent you, by law, must have both signed and received a paper copy of, not blank, but copied after you signed. This issue will be spelled out. If you can't find your consent call your coordinator and request a copy. Investigators (the doctors who run trial sites) MUST keep this document with your original signature - it's an FDA requirement, and all human trials must follow FDA guidance. It's also entirely possible that subjects who received placebo will be offered the vaccine if the test vaccine is later FDA approved - I've seen this in some trials. It will, again, be spelled out in the Informed Consent.

Some trials are designed to unblind and inform the subjects which arm of the study they were assigned to, but not all. I haven't coordinated vaccine trials, and perhaps these are different: it certainly should be designed to inform subjects, ethically. Otherwise how will subjects know if they have vaccine-induced immunity or if they need to get immunized? If they do unblind and inform you, the bigger question is probably when they will do so. Often unblinding is done way, way after the trial is completed, all the statistical slicing and dicing is done, after the principal investigators write their peer-reviewed papers and the test article (medication, vaccine, medical device) is submitted for FDA approval - and approved. One trial I coordinated didn't inform us which subjects were in which arm until more than 2 years after the study was concluded. Clearly, this will not work for a vaccine.

The short answer is that it should be easy to find out what the plan is for unblinding, and it will be spelled out in the Informed consent.
posted by citygirl at 2:59 PM on November 14, 2020 [4 favorites]


I'm in a covid vaccine trial right now and asked some of these questions during the screening process. Happy to chat about my experience, feel free to message me.
posted by miskatonic at 11:21 AM on November 17, 2020


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