What Are the Differences Between the Leading Coronavirus Vaccine Candidates?

All of the leading coronavirus vaccine candidates share one quality: They seek to spur the body's immune system to fight future infections of the virus that causes COVID-19. However, how they try to accomplish this goal varies from one vaccine to another. In this Fool Live video, Healthcare and Cannabis Bureau Chief Corinne Cardina and longtime Motley Fool contributor Keith Speights discuss the main differences between the leading coronavirus vaccines in development.

Corinne Cardina: So let's get into the stocks. Of course, before we get into the stocks, I think it will be helpful to set the stage for the different approaches that these different companies are taking for their vaccine. Could you explain briefly, without getting too much into the weeds of the science of course, how the different vaccine developers are approaching conferring immunity, I'd be happy to list them out or you can list them as we go.

Keith Speights: Sure. I can speak to that. Let me just first say that all of the vaccines have the same underlying goal, and that goal is to trick the body's immune system into thinking that it's fighting a full-blown attack from the coronavirus. So all of them want to do that, but what differs is how they trick.

There are different methods of trickery and you've got two of the leading candidates, Pfizer (PFE -3.85%) and BioNTech (BNTX -1.57%), as well as Moderna (MRNA -2.45%), use a similar approach using a nucleic acid called messenger RNA, and so that's one of the top approaches. There's also another nucleic acid approach called DNA vaccines. I don't think any of the leading candidates right now are DNA vaccines, but we do have a couple at least that are mRNA vaccines.

What those vaccines try to do is they engineer messenger RNA injected into the body, and so that messenger RNA gets into the cells and it carries instructions to the ribosomes, which are the body's protein-making factories, and it tells the ribosome to make a protein that's basically an exact mirror of the spike protein on the coronavirus that causes COVID-19. It's interesting with that approach, no virus actually enters the body whatsoever. It's an artificially engineered protein that's like the virus, then the body mounts an immune system defense to that. That's one approach.

Another approach that a couple of the leaders are using, Johnson & Johnson (JNJ -1.15%) and AstraZeneca (AZN 5.38%) use a viral vector. So what a viral vector is, it basically uses another kind of virus to insert typically a gene into the body to do essentially the same kind of thing, which is try to produce an antigen that's like the coronavirus so that the body mounts an immune defense.

I think both AstraZeneca and Johnson & Johnson are using a virus called adenovirus. AstraZeneca is using a version of that particular virus that actually causes the common cold, and it's one of the main causes of the common cold. They're using a version of the virus that infects chimpanzees. And the reason why they're doing that is the issue with those type of viral vector vaccines is that in many cases, humans have already developed immune responses to those viruses, and so our immune system will begin to attack the virus that's trying to deliver the gene. And so that's why AstraZeneca, for example, is taking the chimpanzee virus approach because our bodies wouldn't reject it as quickly.

I should note though that both AstraZeneca and Johnson & Johnson also have another thing in common. Both of them have had to put clinical trials on pause because of an unexplained illness with the participants. So it's unsure if that's really related to their method or not, we really don't know, but that is another common denominator those two vaccines have.

And then you have another approach called the sub-unit approach. Sometimes you'll hear it referred to as protein subunit. An example of a company that's doing this is Novavax (NVAX -4.82%). And what Novavax is doing is they inject -- basically when you look at it is just pieces and parts kind of approach where they have a part of a protein of the coronavirus injected into the body and then the immune system mounts a defense against it.

Then lastly, there is the traditional approach of just using a weakened or inactivated virus. That's where your body actually does fight the virus. Now, none of the five leaders that are in late-stage testing that are factors in the U.S. market are using that approach, but I think at least maybe one of the Russian drugmakers may be using that approach.