On Wednesday, the Food and Drug Administration granted Emergency Use Authorization for boosters of Moderna's (NASDAQ:MRNA) COVID-19 vaccine. This decision came despite the fact that briefing documents prepared by the FDA for an advisory committee's review of Moderna's booster data weren't overly enthusiastic. In this Motley Fool Live video recorded on Oct. 13, Motley Fool contributors Keith Speights and Brian Orelli discuss why the FDA isn't thrilled about Moderna's COVID-19 boosters.

Keith Speights: There's an FDA advisory committee that's going to be meeting this week to review Moderna's COVID-19 vaccine booster data. The FDA released its briefing documents in advance of that meeting on Tuesday, which is par for the course for the FDA, that's what they usually do. It appears that the FDA isn't necessarily all that thrilled about Moderna's booster.

Now, the briefing documents didn't come out against the booster, but it didn't seem that they were gung ho about it either, so what's the story here?

Brian Orelli: I don't think the issue is really about whether the booster actually works, clearly, it raises the antibody levels, which is what a booster is supposed to do. It's not about the safety either, it looks like it's about the safest as the second dose. The issue, I think, is mostly about whether it's needed.

Just because you have lower antibody levels six months after your second dose doesn't necessarily mean that you're not protected. There's obviously some level where that's true, but there's multiple factors that go into it. How much virus are you exposed to. If you're exposed to less virus, then you obviously need less antibody to counteract those viral particles that you get exposed to.

Then how good is your immune system to reacting to the virus. Beyond your antibodies, you have memory B cells and memory T cells, and those will take over eventually and take care of the virus assuming you've been vaccinated or to a lesser extent if you've been exposed previously to the COVID-19 virus. Then the lower level of antibody really doesn't tell you anything about the likelihood of severe disease. Just because you have lower levels and you might get infected and you might get cold-like symptoms doesn't necessarily mean that you're going to end up in the hospital, and that's really what we should be trying to prevent.

That's the FDA's argument. It's basically the same argument that they made for Pfizer (NYSE:PFE) and BioNTech's (NASDAQ:BNTX) booster. The Advisory Committee there came to the conclusion that it made sense to give the vaccine to the people who were at most risk, people who are highly likely to be exposed to somebody with COVID-19 or somebody who's less likely to get exposed to COVID-19, but if they did get exposed, would be more likely to end up in the hospital.

I think that's the right move and I think the committee ultimately, and the FDA will ultimately do the same thing here. It should be noted that the CDC's advisory committee that reviews approvals after the FDA approves a vaccine, the CDC's committee meets and makes recommendations on who the approved vaccine should actually be used for. They're advising doctors here. That meeting has already been scheduled for Moderna's booster. Clearly, the CDC is assuming it'll get approved by the FDA.

Speights: I think it's not just you and the CDC anticipating this authorization, Moderna's stock is up this morning around 4%. I think investors, in general, are pretty much banking on this authorization going through.

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