Moderna(NASDAQ:MRNA) stock skyrocketed last year. Its momentum has carried over into 2021 as well. After its tremendous gains, the biotech's market cap is now well over $60 billion. In this Motley Fool Live video recorded on Feb. 3, 2021, Fool.com contributors Keith Speights and Brian Orelli talk about whether Moderna stock is now overvalued after its remarkable run.

Keith Speights: Bank of America downgraded Moderna this week to underperform from neutral. Agree or disagree with this move?

Brian Orelli: I mean, I've been saying Moderna was overpriced for months now. I was not wrong, so I don't know. I mean, I think it's a really high valuation with its [...] market cap. I think, if you assume $15 billion in sales, that's a price-to-sales ratio of 4. That's pricing it like they're not going to continue to earn $15 billion in sales or that they're going to have $15 billion in sales continuing but it's not really going to grow much beyond that for the foreseeable future. I think that's a reasonable valuation if you assume that they're going to be able to continue selling coronavirus vaccines and or get the rest of their pipeline into sales fairly quickly.

Speights: It's important to remember that Wall Street analysts are looking at the short term, and over the short term, Moderna probably doesn't have many catalysts that are going to bump that stock much higher. Over the long term, they could be a platform company with their messenger RNA technology and so I think investors should keep that in mind. Differentiate between short-term thinking and long-term thinking with any stock but especially a stock like Moderna.

Orelli: Yeah. I think if you're going to buy it, you have to be planning on buying it for a while, because it certainly could go down from here before it goes higher.