If you receive the first dose of one company's COVID-19 vaccine, you get a second dose of that same vaccine. However, "mix-and-match" clinical studies are under way that are evaluating how well a second dose of a different vaccine might work. And some early results for this approach appear to be promising. In this Motley Fool Live video recorded on May 26, Motley Fool contributors Keith Speights and Brian Orelli discuss whether or not mixing COVID-19 vaccines will be likely down the road.

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Keith Speights: I did see something interesting, Brian, something just came to the top of my mind. I saw some results from a study conducted in Spain where a combination of the first dose of AstraZeneca's (AZN 0.83%) vaccine with the second dose of Pfizer's (PFE 0.88%) vaccine actually seem to be much more effective, at least created much higher neutralizing antibody levels than the AstraZeneca vaccine by itself, or two doses of Pfizer's vaccine.

It hasn't been peer-reviewed yet. Relatively small study. Who knows if it'll be confirmed. But that's at least interesting to me that some of these mix-and-match possibilities could create some interesting market dynamics here.

Brian Orelli: Yeah, and that makes sense because they're all developing it to the spike protein, which is the outside part that attaches to the cell to inject its RNA into the cell that ends up making more virus. The proteins aren't necessarily exactly the same. They are part of the spike protein but they may not follow exactly the same.

It would make sense that getting more than one vaccine might be beneficial in creating different kinds of antibodies. Then when you're measuring neutralizing antibodies you're basically just throwing all the antibodies in with the virus. That would allow them to bind to different parts of the virus and theoretically have a higher blocking level than in individual.

Speights: There's some other mix-and-match clinical studies going on that I'm sure we'll be talking about some in the future because it could be interesting to see how efficacy varies when you mix and match different vaccines together. I'm not sure that that will necessarily impact the market in a huge way going forward because my hunch is that maybe after some time into next year, that we'll probably transition to single-shot booster doses instead of multiple doses. If that happens as I suspect will happen then these mix-and-match studies might not matter all that much.

Orelli: I think we're probably going to get pretty close to where we are with the flu vaccines, where you go in and get a flu vaccine, but you don't know what brand you got. That's probably true of most vaccines. I think that COVID-19 is probably one of the few exceptions where people actually know what brand of vaccine they got.