Moderna's (MRNA 2.70%) stock has seen better days. Shares of the coronavirus vaccine giant have dropped 30% over the past month. Why the decline? Investors are concerned about diminished demand once the pandemic is over -- and as new COVID-19 treatments come to market. I've written about how that reaction was likely overdone.

Now, investors have turned their attention to something else: A regulatory meeting that could determine whether Moderna's booster candidate reaches the market in the coming days. A U.S. Food and Drug Administration (FDA) advisory committee meets today to discuss the candidate's fate. Could a positive decision lead to a rebound for the stock? Let's take a look.

A group of business people discuss something in a conference room.

Image source: Getty Images.

Moderna's booster request

First, let's take a look at Moderna's request. The biotech company seeks authorization of a half-dose of its coronavirus vaccine to be used as a booster in some individuals. This includes only those who received the primary series at least six months ago -- and these individuals must be ages 65 or older, have a comorbidity if they're younger than 65, or work in a high-risk environment. The FDA authorized Pfizer's booster for this group a few weeks ago.

Strangely enough, Moderna's high efficacy may be an argument against use of its booster. All clinical trial participants had received the primary series six to eight months earlier. And some participants still had high levels of antibodies. In those cases, the booster didn't push antibody levels significantly higher. The booster was most effective in those whose immunity had waned.

On top of that, the FDA doesn't seem to view boosters as a necessity right now. In a briefing document to the committee, the FDA emphasized that Moderna's two-dose vaccine offers solid protection.

Still, I think it's likely the FDA will allow Moderna to move forward with its booster -- as long as the agency is satisfied with the safety and efficacy data. So far, those elements seem satisfactory.

Protection against severe disease

Why am I optimistic? First, the FDA's briefing document ahead of the Pfizer booster decision carried a similar message. In fact, the FDA used the same words in the Pfizer and Moderna documents: "[D]ata indicate that currently US-licensed or authorized COVID-19 vaccines still afford protection against severe COVID-19 disease and death in the United States." And as we know, the FDA went on to authorize the Pfizer booster.

And second, the lack of a Moderna booster may leave many who need a booster without one. The Moderna trial showed that some participants indeed had waning immunity. And these individuals can't just go out and get the Pfizer jab. The FDA authorized Pfizer's booster only for those who received the Pfizer primary series.

Of course, the FDA could refuse Moderna's request for authorization. This is the biggest immediate risk for Moderna. For reasons I mention above, I think this is unlikely. But it's still something investors should consider before buying the stock right now.

Moderna's share price

Now, let's turn to the Moderna share price. Could the authorization of a booster offer the stock a lift? Possibly. But I don't expect a huge movement in the shares. Here's why: I think many investors are expecting Moderna's booster to reach commercialization in the coming weeks. The news wouldn't be a surprise.

Also, a booster doesn't mean more revenue immediately. Moderna has already signed supply agreements for this year. So this won't increase product sales in the near term. As a result, investors may not consider the booster a reason to push the shares much higher right now.

But here's the good news for those of you who are holding onto Moderna for the long term. A booster would represent an increase in revenue down the road. It means people would need three shots instead of two. And the lower dose of the booster means Moderna can produce more units of product.

This FDA decision may not be critical for near-term earnings or share performance. But a booster could play a significant role in both a bit further down the road.