A single dose of Pfizer (PFE -1.82%) and BioNTech's (BNTX -0.61%) coronavirus vaccine may offer some protection against COVID-19. But it's still too early for investors in the coronavirus vaccine companies to worry about the potential revenue being cut in half. In this video from Motley Fool Live, recorded on Feb. 22, Fool.com contributors Brian Orelli and Keith Speights discuss why one dose isn't likely to be recommended in the U.S.

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Keight Speights: Brian, there was one intriguing finding, I also noticed in that report last week and it was that Canadian researchers found that Pfizer's vaccine was nearly as effective after only one dose as it was with two doses given one month apart, I think they were showing 92.6% efficacy based on the data they were looking at. They were even recommending postponing the second dose of the Pfizer shot. This is a similar finding that Israeli researchers found. They looked and saw not quite as high of an efficacy, but they still found that the efficacy for the Pfizer vaccine after the first dose was higher than originally thought. Still too early to know about all of this, whether or not all this is going to pan out but I thought that was really intriguing.

Brian Orelli: Yeah. I think it's hard to know exactly how long it's going to last, they're measuring fairly short windows, and so the question is, how long can you delay that second dose and still feel like you're covered? I think that sounds like the FDA has definitely going to not recommend that and will stick with two doses on a regular schedule.

Speights: My mom called me last week and she and my dad had their first vaccine, the Pfizer vaccine and she said, "Hey, I saw this on the news about this. Do you think I want to have to take the second shot?" I said "No, mom, you're going to have to take the second shot" [laughs] and so you want to take the second shot?

Orelli: Almost even want to feel bad because if you feel bad then your body is having nice strong reactions.

Speights: That shows it's working.

Orelli: Ironically, I think it probably means that you're more likely if you get a strong response it means you're more likely to have not needed the dose and then if you don't get a strong response that means you probably needed the booster, but you won't know that until you take vaccine the second dose and it's too late at that point.