New Year's celebrations are likely to look a lot different this year than most, as many people heed warnings to steer clear of mass gatherings during the global COVID-19 pandemic. Wall Street also seems to have had some cold water thrown on what was otherwise an extremely strong year for the stock market, as major market benchmarks are down at midday on New Year's Eve. As of noon EST, the Dow Jones Industrial Average (DJINDICES:^DJI) was down 39 points to 30,370. The S&P 500 (SNPINDEX:^GSPC) lost 3 points to 3,729, and the Nasdaq Composite (NASDAQINDEX:^IXIC) eased lower by 36 points to 12,834.

Yet even with the markets losing ground, several of the year's best-performing individual stocks kept up their momentum. Shares of Fulgent Genetics (NASDAQ:FLGT) and Celsius Holdings (NASDAQ:CELH) have already soared in 2020, but investors were willing to put more money to work and send their share prices still higher on the final day of the year.

FLGT Chart

FLGT data by YCharts.

Fulgent has never looked healthier

Shares of Fulgent Genetics were up more than 10% on Thursday at midday. The genetic testing and diagnostics company has gotten a lot of business from the pandemic, and Fulgent continues to pull in customers and demonstrate its value to shareholders.

Fulgent found itself in the right place at the right time in 2020, with its quick work in coming up with coronavirus tests leading to an at-home sample-collection kit that received approval from the U.S. Food and Drug Administration in June. The company's third-quarter revenue skyrocketed as a result, topping the $100 million mark after doing just $10 million in business in the same period of 2019.

Blue glove holding red vial marked COVID-19.

Image source: Getty Images.

Some fear that now that coronavirus vaccines are available, Fulgent will see its COVID-19 testing fall off a cliff. However, with the rollout of vaccines going at a slower pace than many had hoped for, there'll still be plenty of need for coronavirus tests well into 2021. And more importantly, with Fulgent having demonstrated its ability to respond quickly in a crisis, the company has made valuable contacts in the healthcare and insurance industries that should serve to produce further growth opportunities in the years to come.

Fulgent has more than quadrupled investors' money in 2020. It might not jump another 300% or more in 2021, but the genetic-testing specialist has plenty of chances to keep its stock moving higher.

Feeling energetic

Shares of Celsius Holdings fared even better, rising more than 13% at midday. That's consistent with what's been an amazing year for the energy-drink specialist, with its stock jumping to more than 10 times where it started the year.

The latest surge for Celsius came as a result of a move from index managers at S&P Dow Jones Indices. Celsius will join the S&P SmallCap 600 Index effective as of Jan. 7. The move stems from an acquisition involving a company in the S&P 500, which created a cascade effect that eventually created a vacancy in the small-cap index.

Celsius joined a highly competitive arena with its energy drinks, but the company's focus on fitness and performance resonated well with consumers. Revenue has jumped more than fivefold in less than four years, and Celsius turned profitable in 2019 and has managed to maintain its bottom-line strength, even in the difficult current environment. That's a big part of what's attracting attention for the company, and it holds the key to Celsius' future success.

What's next for these winners?

Investors must not get used to seeing stocks climb 300%, 500%, or even 1,000% in a year. However, when it happens, it often signals strength that will continue. Investors should expect to see more good things from Celsius and Fulgent in 2021.

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.