What happened
Shares of Moderna (MRNA 0.66%) were 5.4% lower as of 10:36 a.m. EDT on Wednesday even though the biotech didn't announce any news that would cause its shares to fall.
So what's the culprit behind today's decline? Biotech stocks are sliding in general. The two major biotech exchange-traded funds (ETFs) -- iShares Nasdaq Biotechnology ETF and SPDR S&P Biotech ETF -- are both down, as investors appear to be nervous because of the Federal Reserve Board meeting today.
So what
There's a simple reason biotech stocks (and other stocks as well) are volatile ahead of the Fed's conclusion of its two-day meeting: It's possible that the central bank could raise interest rates. If that happens, stocks would be less attractive to investors in comparison to other assets such as bonds because yields increase as interest rates increase.

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Moderna likely fell harder than some other biotech stocks because investors think it's valued at a premium price. The important thing to recognize, however, is that Moderna's fortunes depend much more on the demand for COVID-19 vaccines after 2021 and the company's pipeline progress than they do on interest rate fluctuations.
Now what
Moderna has a couple of clinical studies underway that investors will want to watch closely. It's evaluating COVID-19 vaccine mRNA-1273 in a phase 2/3 study in children between ages six months and under 12 years. The biotech is also evaluating a next-generation COVID-19 vaccine, mRNA-1283, in an early-stage clinical study. This vaccine candidate could be stored at standard refrigerator temperatures and could potentially be a single-dose regimen.