Don't just assume a stock that has amassed large gains over months or even years has hit its peak. It may have only taken a breather before heading higher still.

Three Motley Fool contributors believe Novavax (NVAX 1.16%), A.O. Smith (AOS 2.03%), and XPO Logistics (XPO 2.15%) are just such businesses, companies that exhibit all the signs of being growth stocks that still have a lot of room to run.

Man turning dial labeled "sales" to "high."

Image source: Getty Images.

A small-cap biotech with big plans

George Budwell (Novavax): Novavax is a clinical-stage vaccine company that has all the ingredients necessary for success. Kicking off the first quarter, the company has already released a promising update for its next-generation flu vaccine, NanoFlu, in older adults. This mid-stage trial success could turn out to be the foundation for an accelerated filing, or at a minimum, it should pave the way for a late-stage trial to get underway later this year.

The big deal is that NanoFlu is targeting a massive $3 billion-a-year commercial opportunity. Novavax would thus only need to capture a tiny fraction of this ginormous market for NanoFlu to be a major growth driver for the company.

Novavax is also pursuing another monstrous growth opportunity with its late-stage respiratory syncytial (RSV) virus vaccine program. After four long years, the company is finally nearing a top-line data readout for its maternal RSV immunization study later this quarter. This pivotal trial -- if successful -- would catapult the company into the realm of commercial-stage biotechs and likely transform it into a cash-flow-positive operation within a few short years. After all, RSV is a multibillion-dollar-a-year market in its own right, and there are no products currently approved for this particular indication.

Given that Novavax has two blockbuster vaccine candidates under development at the moment and both are reportedly proceeding according to plan, this small-cap biotech stock is clearly capable of producing stellar returns for investors this year. In fact, Wall Street's current 12-month price target implies that Novavax's shares could more than double in 2019. To unlock this jaw-dropping value scenario, though, the biotech will have to do something it's never done before: report positive late-stage trial results. And if it fails to do so yet again, Novavax's enormous potential as a growth stock could evaporate literally overnight.

Check out the latest Novavax earnings call transcript.

You just can't miss this opportunity

Neha Chamaria (A.O. Smith): A.O. Smith shares took a deep breather in 2018 after a run-up that lasted several years. You only have to see this graph to understand what I'm talking about.

AOS Chart

AOS data by YCharts.

So what would it take for the stock to rally again? Not much, I'd say, except that the manufacturer of water heaters and boilers should continue doing what it does best: earn strong returns on invested capital, prudently allocate capital, and reward shareholders consistently. There are several strong reasons to believe A.O. Smith will deliver.

First, A.O. Smith gets a little more than one-third of its sales from international markets. While strong replacement demand should remain a steady revenue generator in North America, booming middle classes and urbanization in nations like China and India should create a big market for water heaters and water treatment solutions. China is already a compelling growth story for the company, with its sales from the nation recently hitting $1 billion after growing at a compound annual rate of nearly 21% in the past decade.

Second, A.O. Smith is open to pursuing acquisitions to complement organic growth, backed by a rock-solid balance sheet characterized by low debt and strong cash flows. Third, A.O. Smith is an excellent dividend payer: It increased its dividend twice in 2018 and has grown it at a compound annual clip of 30% in the past five years. The stock currently yields 2%.

From what I see, A.O. Smith is a growth company and should continue being one. As the company delivers in coming years, its stock price could soar, making the recent drop look like a rare opportunity in hindsight.

Check out the latest A.O. Smith earnings call transcript.

Keep on truckin'

Rich Duprey (XPO Logistics): XPO Logistics has had a tremendous growth story since its inception, and over the past decade, its shares have returned more than 1,300% as demand for freight transportation and logistics services soared. Even though shares lost about half their value from their high point three months ago, XPO is turning things around again and is poised for another run higher.

Nearly 71% of all the freight tonnage in the U.S. travels via truck, which requires more than 3.5 million truck drivers to move it. But the looming driver shortage has weighed on trucking companies, and not just XPO. The company is the second-largest freight brokerage provider globally, is the leader in Europe and North America, and is also the largest provider of last-mile deliveries for heavy goods.

In response, XPO has launched a number of initiatives to offset the strain, particularly its ambitious XPO Direct program, a shared-space distribution model that combines its distribution centers, less-than-truckload shipping, and local delivery services into a cohesive whole so that shippers don't have to pay for their own distribution centers. They can rent own XPO Logistics' vast storage space and delivery vehicles to fulfill last-mile consumer demand.

Even in the face of tougher times, analysts forecast XPO Logistics will double its earnings this year and see them rise another 25% next year and have a long-term forecast of earnings expanding 38% annually for the next five years.

As the industry leader that's implementing unique strategies to surmount the speed bumps in its way, XPO Logistics is indeed a growth stock that's only just getting started.

Check out the latest XPO Logistics earnings call transcript.