The ongoing COVID-19 crisis is making its way up the list of the most deadly pandemics in human history, with more than 1 million people killed as of Oct. 7. As a second wave of infections spreads across the western world, potential vaccines and treatments are in the spotlight -- and the stocks of the businesses working on them have once again captivated investors' attention. 

There are a lot of good coronavirus stocks out there -- so many that investors may feel overwhelmed by the choices. Fortunately, there are three companies right now with particularly great potential to reward investors who are in it for the long term. Let's take a look at them. 

Photo of COVID-19 sign beside a commercial aircraft.

Image source: Getty Images.

1. Pfizer

On Oct. 6, the European Medical Agency (EMA) announced the commencement of its accelerated approval process for Pfizer (NYSE:PFE) and BioNTech's (NASDAQ:BNTX) messenger RNA COVID-19 vaccine candidate, BNT162b2. The experimental vaccine is currently in phase 3 studies, with more than 28,000 out of 37,000 participants having completed their final dose.

In phase 1/2 testing, as well as preclinical studies, participants who took BNT162b2 developed neutralizing antibodies, which are small proteins that recognize specific components of a pathogen and prevent it from invading healthy cells. Moreover, all participants also developed SARS-CoV-2-specific T-cell responses after dosage. T-cells recognize virus-infected cells and tell those cells to self-destruct, preventing the virus from spreading throughout the body. Unlike antibodies, which may disappear just weeks after dosage, T-cells can form memories of pathogens for months or years.

That is undoubtedly excellent news, and the recent priority review by the EMA certainly helps build the bull case for the stock. Even before the full clinical trial results are out, governments worldwide have placed their faith in both companies' science. Pfizer and BioNTech are currently finalizing a deal with the E.U. to supply the supranational organization with 200 million doses of BNT162b2, and the two companies previously secured orders from the U.S. government (for up to 600 million doses), the Japanese government (for 120 million doses), the U.K. government (for 30 million doses), and the Canadian government (for an undisclosed amount).

At a price tag of $19.50 per dose, that's a potential $18.5 billion worth of revenue in the bag, split between the two companies. By the end of next year, Pfizer and BioNTech expect to produce up to 1.3 billion doses of BNT162b2 if it is approved.

Meanwhile, Pfizer is very well capitalized, with a debt-to-equity ratio of just 0.36. A debt-to-equity ratio of less than 1 indicates a company's assets are more than enough to sustain its liabilities. For all its growth opportunities ahead, Pfizer stock is surprisingly cheap by several measures; in fact, the company trades at a mere 4.2 times price-to-sales (P/S) and 14.6 times price-to-earnings (P/E), while boasting an impressive dividend yield of 4%, more than twice the S&P 500 average.

2. Regeneron Pharmaceuticals

Regeneron Pharmaceuticals (NASDAQ:REGN) once again entered the spotlight early in October when President Trump received the large-cap biotech's experimental antibody cocktail, REGN-COV2, to treat his coronavirus infection. It's theorized that REGN-COV2 alleviates symptoms of the deadly disease, as well as reducing its viral load.

To date, the company has received $450 million as part of the Trump administration's Operation Warp Speed to advance coronavirus vaccines and treatments. Its core business has also been performing well, with record growth in drugs including Eylea (for eye diseases), Dupixent (for eczema, asthma, and more), and Libtayo (for skin cancer).

Back in 2006, Regeneron had just $65 million in annual revenue and posted a net loss of $9.6 million. As of Q2 2020, the company's trailing-12-month revenue and net income have increased to a staggering $8.7 billion and $3 billion, respectively. 

What's more impressive is that the company achieved such outstanding growth while accumulating just $1.5 billion in long-term debt. As of now, Regeneron is trading for 8.7 times price-to-sales and 23.4 times price-to-earnings. Although those may seem like hefty premiums, keep in mind the company is still very cheap compared to its potential. 

3. Zoom Video Communications 

Ever since the coronavirus pandemic began, Zoom Video Communications (NASDAQ:ZM) has been at the forefront of digitizing workplace conferences, making video streaming easy for employees who need to work remotely. By the end of Q2 2021, there were 370,000 businesses with more than 10 employees using Zoom's services, an increase of 458% year over year. At the same time, the company has nearly resolved the privacy issues that had allowed strangers to interrupt ongoing calls, restoring confidence in the platform.

During the quarter, Zoom's revenue was up 355% over last year to $663.5 million, while its earnings per share (EPS) increased more than 30-fold to $0.63. The company's growth streak is far from over, however, as the digital reopening of schools and universities has created significant demand for the service from instructors offering online video lectures. For tech investors looking for companies with substantial growth, they should look no further than Zoom.