In this video from Motley Fool Live recorded on Feb. 1, Fool.com contributors Brian Orelli and Keith Speights discussed phase 3 clinical trial data on Novavax's (NASDAQ:NVAX) coronavirus vaccine. The vaccine worked as well as the vaccine from Moderna (NASDAQ:MRNA) and the one from Pfizer (NYSE:PFE) and BioNTech (NASDAQ:BNTX) against the original strain of the coronavirus. More importantly, Novavax's vaccine appears to protect participants from the U.K. variant, albeit to a lesser extent.

Brian Orelli: Moving on to our second story, Novavax also released phase 3 data last week. This was from a clinical trial in the United Kingdom. It had 89.3% efficacy. The U.K. variant was found in over 50% of the cases of COVID-19, so it seems it's doing fairly well. They did a post-hoc analysis. This is not hypothesis driven, this is looking after the fact; after you get the data you say, "What else can we analyze about it?" But they found that the vaccine was 95.6% effective against the original COVID-19 strain, and they estimated it would be 85.6% effective against the U.K. variant. It seems pretty good and pretty solid data and pretty good at least for the U.K.'s variant that the efficacy is all the way up at 85%. That was better than Johnson & Johnson's (NYSE:JNJ) which was at 66% for Latin America, and 67% South Africa.

Keith Speights: I thought Novavax's results were outstanding. I think they had a high bar to meet and they met it. The safety profile looked very good as well. I think Novavax did what they needed to do. If you're trying to compare apples-to-apples which is next to impossible to do. But in that post-hoc analysis as you mentioned, they had the 95.6 efficacy against the original COVID-19 strain. Well, if you're trying to compare apples-to-apples, that might be the number you might lean toward using, so it puts it right in the ballpark and maybe even a little better than the Pfizer and Moderna vaccine. I think Novavax just hit a home run with their results.

Orelli: Just to remind people, this is nanoparticle, there's a small fat molecule you can imagine, and then they put the protein on the outside of the nanoparticle, and then they have the adjuvant which increases the immune reaction to the protein on the outside of the nanoparticle.

Novavax also released phase 2b data from a study in South Africa and it had 60% efficacy in HIV negative participants; if you look at the overall participants including the HIV positive ones, it was down to 49.4%. But I think the 60% is probably a better thing to look at when you're looking at the total population. Then 92.6% of those were South African escape variants. Fairly decent efficacy against the South African variant comparing 60% for Novavax back to Johnson & Johnson, which was 57% -- so in the same range.

One thing I did note, it was stuck at the bottom. I don't know if you noticed this, but some of the participants that had COVID-19 antibodies before the clinical trial started, and then they got COVID-19 again with the South African variant. That implies that the first COVID infection isn't necessarily going to protect you against the second one, especially with the South African variant. But we also saw that in Pfizer study and maybe even Moderna study where some of the participants had antibodies and then they got COVID again. It seems to be how much of a reaction we get the first-time around, that determines how much antibodies you have, and then that might determine whether you're actually protected against the second infection.

Speights: How you look at the phase 2b study results from Novavax, how you look at those results probably depends on whether or not you see a glass of water, half-full or half empty. If you are the pessimistic type, you're going to look and see, "Wow, the efficacy dropped off dramatically with the South African variant," and it did. But if you're more positive and optimistic, you are going to look and say, "Yeah, but it's still achieved," as you said Brian, "the 60% efficacy and the HIV negative participants." That's still really good and certainly provides protection and help slow the spreads, so Novavax's vaccine is effective against this more troublesome variant, it's just not as effective. I think the company is going to move forward with a booster dose that's targeting that particular variant and maybe not just the South African variant, but I know they're looking at moving forward with an additional study of a booster dose to hopefully, maybe boost the efficacy against this particular strain.

Orelli: Yeah, I think they're doing both. They're going to have a third booster with the original construct. Then they're also designing a new construct that would include some of the variance in it and then hopefully, that would provide protection against the variants as well.

Speights: I think Moderna said they're going to do something similar as well. We will have more news probably several months from now about potentially vaccine versions that can be more effective against the South African variant.

Orelli: Right. Yeah, I was talking about Moderna's.

Speights: Oh, Moderna. Okay, sorry.

Orelli: Yeah.

Speights: Actually, I think Novavax might be doing the same thing though.

Orelli: Oh, really. Yeah. Okay. I definitely missed that.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.