Since the end of the Great Recession over 12 years ago, growth stocks have been the talk of the town on Wall Street. The combination of historically low lending rates and ongoing quantitative easing measures from the Federal Reserve has made capital cheap and abundant for fast-paced companies. This is why growth stocks have had no trouble running circles around value stocks.

But for some high-flying growth stocks, significant upside awaits, depending on the analyst or investment bank you ask. Although the following trio of growth stocks have already soared in value over the past couple of years, the high-water price target on Wall Street for each implies they'll more than double in value over the coming 12 months.

A person using a stylus to interact with a rapidly rising stock chart displayed on a tablet.

Image source: Getty Images.

Moderna: Implied upside of 112%

The first highflier that at least one Wall Street firm believes could more than double is biotech stock Moderna (MRNA -0.15%). Despite gaining almost 1,100% since the beginning of 2020, Wall Street's peak price target of $490 over the coming year suggests it could shoot higher by another 112%.

Chances are that most people are familiar with the Moderna name. It's been one of the key players on the coronavirus disease 2019 (COVID-19) vaccine front. The company's vaccine, mRNA-1273, demonstrated a vaccine efficacy (VE) of 94% in U.S clinical studies in November of last year. Few other COVID-19 vaccine candidates have come close to mRNA-1273's initial VE, which is what's made it such a popular vaccine choice with the public.

Although it isn't clear how we as a society will adapt to COVID-19 moving forward, the mutability of the SARS-CoV-2 virus that causes COVID-19, as well as the need to vaccinate billions of additional people worldwide, is creating a need for initial inoculations and, likely, booster shots. Should COVID-19 vaccines become necessary each year, Moderna would have itself a recurring revenue stream.

What's more, Moderna is one of a small handful of drug companies looking to develop a combination vaccine for influenza and COVID-19. Being able to prepare people for two potentially deadly ailments each year could give Moderna a leg up on its growing competition.

However, I'd be remiss if I didn't point out that Moderna's only sustaining revenue stream is from its COVID-19 vaccine. If booster shots aren't necessary beyond 2022, the company's sales could shrink rapidly. Between new vaccine entrants, oral vaccine innovation, and Moderna's whopping $94 billion market cap, there seems to be a lot of risk baked into this valuation.

A person using a tablet to make an online sports wager on a soccer match.

Image source: Getty Images.

Penn National Gaming: Implied upside of 123%

A second high-flying growth company with some serious projected upside is Penn National Gaming (PENN -0.27%). Even with Penn National's share price surging 128% to $58.25 since the beginning of 2020, one Wall Street firm foresees it reaching $130 over the next 12 months. For those of you keeping score at home, this works out to an implied upside of 123%.

The buzz surrounding Penn National Gaming has to do with its push into online sports betting and iGaming, which includes online video games and other types of online casino betting. Specifically, investor buzz hit a boiling point last year when the company announced it was acquiring a 36% equity stake in Barstool Sports. This deal was viewed as a way for Penn National to break free from its reliance on its traditional casino operations and firmly move into the online betting/gaming arena. Though estimates vary wildly on Wall Street, online sports betting could be an up to $19 billion opportunity by mid-decade. 

Even though sports betting and iGaming are viewed as Penn National's ticket to faster growth and improved profitability, it can't be overlooked that the company's physical presence has helped it outperform most traditional casino operators during the pandemic. Despite Hurricane Ida and pockets of the COVID-19 delta variant adversely impacting some of its properties in the third quarter, Penn National has done well due to its gaming properties being located away from major tourist hubs.  With plenty of local appeal, Penn National simply hasn't seen the wild ups-and-downs of Macao or Las Vegas.

But just like Moderna, there's another side to this story. For instance, Barstool Sports founder Dave Portnoy was recently hit with sexual misconduct allegations, according to a Business Insider report. With Portnoy the face of the Barstool brand, and Penn National counting on its recently launched Barstool Sportsbook app to drive growth, things are suddenly in flux until these legal claims are resolved.

Further, as my colleague Travis Hoium recently pointed out, Penn National Gaming is late to the party and may not have the momentum it needs to gobble up iGaming market share. Suffice it to say, hitting a share price of $130 in 12 months is unlikely.

A Nio EC6 crossover SUV on a display pedestal in a showroom.

The all-electric Nio EC6 made its debut in the summer of 2020. Image source: Nio.

Nio: Implied upside of 104%

The third high-flying stock that still offers abundant implied upside is electric-vehicle (EV) manufacturer Nio (NIO -1.76%). With a currency-converted peak price target of nearly $87, the expectation for the most bullish Wall Street investment firm is 104% upside from where Nio shares ended the previous week. Mind you, Nio shares are already up 961% since the beginning of 2020.

The clear-cut growth driver for Nio is the need to fight climate change. One of the easiest ways to reduce long-term carbon emissions is to replace fossil fuel-burning vehicles with cleaner automobiles, such as EVs. Nio gets an added boost by being located in China, the world's largest auto market. By 2035, approximately half of China's annual vehicle sales should be powered by alternative energy (EV's and, to a far lesser extent, hybrids).

Innovation certainly seems to be driving demand. In two years, quarterly deliveries have effectively tripled from 8,224 in Q4 2019 to 24,439 in Q3 2021.  Nio has made a habit of introducing a new premium EV annually. Last year's rollout of the EC6 crossover SUV has provided a nice bump up in deliveries.

To build on this point, Nio also introduced its battery-as-a-service program in 2020. In exchange for a monthly fee, buyers receive a discount on the upfront cost of their new Nio EV, as well as the ability to upgrade or replace batteries in the future. Although Nio is giving up some near-term revenue, it's being replaced by high-margin subscription sales that'll ultimately boost brand loyalty.

The biggest concern for the company is how long it's going to take for global supply chain issues to resolve. Nio and its peers are all suffering from semiconductor chip shortages, which is directly impeding production and expansion opportunities. Management would like to get Nio's output to an annual run-rate of 150,000, but it could be a while before this expansion becomes a reality.