Robinhood investors really like coronavirus stocks right now. Nine of the 100 most popular stocks on the trading platform are for drugmakers developing experimental COVID-19 therapies or vaccines.

One of those coronavirus stocks, though, stands head and shoulders above the rest in terms of popularity among Robinhood investors -- Moderna (NASDAQ:MRNA).

Is the biotech stock worthy of its lofty ranking? There's a pretty good argument to be made that it is. Here are three reasons to buy the most popular coronavirus stock on Robinhood.

Coronavirus with $100 bills in the background

Image source: Getty Images.

1. Its coronavirus vaccine

You probably won't be surprised that the top reason to buy Moderna is its coronavirus vaccine candidate, mRNA-1273. The company's experimental messenger RNA (mRNA) vaccine is currently one of only four COVID-19 vaccines that are being evaluated in late-stage clinical studies in the U.S.

It's still too soon to know if mRNA-1273 will be both safe and effective. However, we'll known in the near future: Moderna expects to submit for FDA emergency use authorization (EUA) on Nov. 25, if all goes well in its late-stage clinical trials.

Assuming that Moderna does win regulatory clearance for mRNA-1273, the company stands to rake in a lot of money. It's lined up an agreement with the U.S. government to supply 100 million doses of the vaccine for $1.525 billion. That deal also includes an option to supply another 400 million doses of mRNA-1273. In addition, Moderna has either finalized or is in the process of finalizing supply agreements with the European Commission, Canada, and Japan.

2. Its pipeline

While mRNA-1273 deserves all of the attention that it's getting, there's a bigger story about Moderna that many investors could be missing: the biotech's pipeline.

With mRNA-1273, Moderna inserts RNA into the recipient's cells. It's engineered to instruct the ribosomes in those cells to produce an exact copy of the spike protein on the surface of SARS-CoV2, the novel coronavirus that causes COVID-19. The body's immune system then learns how to fight this antigen. Moderna is counting on this method building immunity against infection by the actual coronavirus.

The company firmly believes that if this mRNA approach works with COVID-19, it will work with a wide range of vaccines targeting other viruses. Moderna's pipeline currently includes six other mRNA vaccines. The mRNA strategy isn't limited to just viral diseases, though: Moderna also has seven other clinical-stage candidates using mRNA to target indications including cancer and coronary artery disease.

If mRNA-1273 is successful (and the signs are pointing to that being the case), Moderna should be in a great position to also achieve success in other diseases. The company's opportunities in other areas could eventually be much greater than its sizable opportunity in COVID-19.

3. Its valuation

You might think listing Moderna's valuation as a reason to buy the stock is ridiculous. After all, the company sports a market cap of $28 billion with no approved product yet to generate revenue. Even including Moderna's revenue from collaborations and grants, the biotech's shares trade at a whopping 234 times sales.

But Moderna isn't nearly as overvalued as it looks at first glance: The company could be only a few months away from having its first blockbuster product on the market. Wall Street recognizes this; analysts peg Moderna's forward price-to-earnings ratio at 20. That's lower than the forward earnings multiple of the S&P 500.

Remember also that any projected earnings figures are based solely on the potential for mRNA-1273. As we've already discussed, though, the coronavirus vaccine could merely be the tip of the iceberg for Moderna -- thanks to the company's deep pipeline and its potential to target even more diseases. Don't be surprised if, in the not-too-distant future, Moderna's current market cap of $28 billion looks dirt cheap in retrospect.