One of the most common reasons people don't start a stock portfolio is that they think they can't afford to invest. While some stocks may not be attainable buys with a smaller starting amount, you can still build your portfolio with a modest initial investment and set yourself up for healthy future gains. If you want to invest $1,000 in the stock market but don't where to start, buying shares of companies that have managed to hold onto strong earnings and profitable product divisions during the pandemic isn't a bad place to start.

Founded in 1849, Pfizer (NYSE:PFE) is a stalwart that has survived many of the greatest financial crises in modern history. The company's coronavirus vaccine candidate is also one of the top contenders in the ongoing vaccine race. French pharmaceutical company Sanofi (NASDAQ:SNY) is another stock that has handled the ups and downs of this year's stock market like a champ. Incidentally, Sanofi also has a promising vaccine candidate in the works. Let's take a closer look at these two fantastic (and dirt cheap) stocks. 

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Pfizer

Pfizer has shown its resilience in the current economic crisis brought on by the coronavirus pandemic. Shares of the pharmaceutical company fell about 27% in the March dip, but have nearly recovered to its starting point at the beginning of the year. The stock's price sits at about $38 as of Aug. 25.

Pfizer is partnering with German biotech BioNTech on its COVID-19 vaccine. As part of the collaboration, BioNTech provided numerous mRNA vaccines from its proprietary platform, while Pfizer put forward its development and manufacturing expertise. The companies currently have their lead vaccine candidate, BNT162b2, in a phase 2/3 safety and efficacy study. The late-stage study will involve up to 30,000 adults, and had already enrolled 11,000 in the trial as of Aug. 20. Pfizer and BioNTech also released positive data from the phase 1 portion of the study on Aug. 20, reporting that BNT162b2 evoked an adequate immune response in participants up to 85 years of age. If the phase 2/3 study continues to show that the vaccine is safe and effective, the companies intend to pursue U.S. Food and Drug Administration (FDA) approval or an Emergency Use Authorization (EUA) designation as soon as October. They are hoping to produce 100 million doses before 2021 and up to 1.3 billion doses next year. In July, Pfizer and BioNTech announced a $1.95 billion Operation Warp Speed (OWS) contract to supply up to 600 million doses of the vaccine to the U.S. government.

Pfizer's balance sheet has shown that, even in the face of the most severe downturn since The Great Depression, demand for drugs and healthcare products is tough to quell. The company amassed $12 billion in revenue and saw 12% operational growth in its biopharma segment during the first three months of 2020. First quarter revenue represented only a 1% year-over-year decline, without taking into account the company's consumer healthcare segment. In 2019, Pfizer merged its consumer healthcare segment with GlaxoSmithKline's (NYSE:GSK)in an unprecedented venture that effectively created a world-class over-the-counter drug titan. Sales of the blockbuster anticoagulant Eliquis also went up 29% in the first quarter of this year and were instrumental in the company's performance early in the pandemic.

In the second quarter, once the pandemic was well under way, the company hit $11.8 billion in revenue. Sales of Pfizer's Vyndaqel and Vyndamax saw 140% operational growth in markets outside the U.S., bringing worldwide revenues to $277 million. Vyndaqel and Vyndamax are drugs used to treat amyloidosis, a disorder that occurs when excess quantities of the protein amyloid cause organ dysfunction. Eliquis sales were up 19% in the second quarter, while breast cancer treatment Ibrance saw an 11% boost in revenue.

Pfizer elevated its revenue guidance for the full-year slightly in its second quarter report, now expecting to fall between $48.6 and $50.6 billion. Another key component of Pfizer's future growth is the merger of subsidiary Upjohn with Mylan (NASDAQ:MYL), which is expected to conclude in the final quarter of the year. When Pfizer announced the merger in July of last year, it noted that the amalgamation of the two companies would effect the following changes:

The new company will transform and accelerate each businesses' ability to serve patients' needs and expand their capabilities across more than 165 markets by bringing together two highly complementary businesses. Mylan brings a diverse portfolio across many geographies and key therapeutic areas...Upjohn brings trusted, iconic brands, such as Lipitor (atorvastatin calcium), Celebrex (celecoxib) and Viagra (sildenafil), and proven commercialization capabilities, including leadership positions in China and other emerging markets.

Pfizer is one of the few companies with a vaccine candidate already in late-stage trials. If BNT162b2 proves safe and effective, Pfizer's star power could surge. But even without a vaccine, Pfizer's diverse portfolio of drugs and acquisition strategy make it a great buy. Its healthy dividend, which currently yields about 3.91%, is just the icing on the cake for this cheap stock.  

Sanofi

Like many other stocks, Sanofi took a sharp dip into bear territory this spring. The stock started to recover at the end of March, and has been trading for roughly $50 since the beginning of April, just behind its highest share price in the trailing 12 weeks ($55). The company pays a dividend of 3.34% and has a market capitalization of more than $64 billion.

Sanofi is working on its adjuvanted coronavirus vaccine in collaboration with U.K.-based GlaxoSmithKline. On July 31, Sanofi announced that the potential vaccine was selected for OWS funding. In return for 600 million doses of the vaccine, the U.S. government paid Sanofi and GlaxoSmithKline $2.1 billion dollars, the largest funding agreement made so far. A phase 1/2 study of the potential vaccine is expected to begin next month, and Sanofi hopes to initiate a phase 3 trial before the year is out. Sanofi and GlaxoSmithKline seek to obtain regulatory approval for the vaccine sometime in the first six months of next year. The companies have also agreed to provide the U.K. government with as many as 60 million doses of the vaccine if it is proven to be safe and effective.  

In 2019, Sanofi saw a 4.8% year-over-year increase in net sales and more than a 9% increase in sales of its vaccines. Although the company's net sales were down 4.9% during the first six months of 2020, Sanofi reported healthy earnings per share (EPS) growth of 9.2% during that period. Sales in the company's Specialty Care segment went up by more than 17%, mainly because of its blockbuster drug Dupixent. The drug earned new approvals in the U.S. and China, and will be used to treat patients with atopic dermatitis. The prescription medication amassed just over $1 billion in sales, a 70% increase from the period in 2019. The company also announced its acquisition of Principia Biopharma Inc. (NASDAQ:PRNB) on Aug. 17, a deal which will significantly augment Sanofi's product pipeline and its research and development (R&D) capabilities.

A successful coronavirus vaccine could be a game changer for Sanofi's future. The competition is stacked -- many other well-funded and resource-rich companies are working on COVID-19 vaccine candidate -- and Sanofi's potential vaccine isn't nearly as far along the trials process as Pfizer's. But if Sanofi's vaccine candidate is effective, there is no reason it can't snag a piece of the pie.

The stock hasn't seen massive gains or losses during the pandemic, and it probably won't make you rich quick. But even without a vaccine, Sanofi is a tried-and-true, cheap value stock you can buy and hold for decades to come.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.