Whether you're a grizzled investor or a baby-faced student of the stock market, small-cap stocks are one of the best places to find major growth for your portfolio. Likewise, if you're a stickler for innovative or disruptive companies, you already know that the healthcare sector is the right place to be. Combine these two concepts, and voila -- you've got a list of spunky and technological stocks that haven't hit it big yet.

In that vein, I've assembled this selection of small-cap healthcare stocks that have blown the door off with growth in the (challenging, unprecedented, etc.) year of 2020. All of the stocks in this list had a market cap higher than $200 million, and lower than $2 billion. Other than that, the factors driving their impressive performance don't have much in common, so let's dive in.

A stock chart in the shape of a burning arrow rising upwards.

Image source: Getty Images.

1. Vaxart

Thanks to the hype surrounding its coronavirus vaccine program, Vaxart (NASDAQ:VXRT) soared around 1,930% this year. Hype aside, the real value in this company is its technology. Vaxart's platform makes shelf-stable oral vaccine tablets that don't require special storage equipment or skilled healthcare workers to administer.

Time will tell whether Vaxart's coronavirus vaccine candidate will succeed in clinical trials, but the company is sitting on a goldmine of technology either way.

2. Co-Diagnostics

Selling millions and millions of coronavirus test kits gave Co-Diagnostics (NASDAQ:CODX) the rocket fuel it needed to grow by more than 1,160% in 2020, and it shows no signs of stopping there. Its most recent quarterly revenue grew by an absolutely astounding 52,559% compared to last year, reaching a total of $47.52 million in trailing income.

And Co-Diagnostics just got the green light from regulators in India to make and sell one of its coronavirus test kits there, paving the way for expansion from its home in the U.S. into a new market. While the company is still quite small, its unabashed success in the pandemic's trial by fire makes this one worth a spot on your watch list.

3. Cardiff Oncology

Cardiff Oncology's (NASDAQ:CRDF) stock gained roughly 1,560% by making progress this year in its fight to treat metastatic colorectal cancer (mCRC) and prostate cancer with its drug onvansertib. In November, Cardiff announced preliminary data from one of its trials in phase 1b/2, which showed that in 91% of the enrolled patients, the drug had controlled their disease. That's excellent news, to say the least, especially because other therapies had already failed where onvansertib succeeded.

But it's important to note that Cardiff's therapy wasn't the only one being used in the trial; the impressive results were made possible through a combination of onvansertib and another drug called bevacizumab. Plus, there's still a lot more research to do in the clinic before the combination therapy will be available for purchase, if it ever is. Though the company isn't profitable yet and won't be anytime soon, investors are excited to see whether these results hold up throughout the rest of the trials. Cardiff could potentially wow the market again next year if they do.

RVP Chart

RVP data by YCharts

4. Celldex Therapeutics

Despite being an early stage biotech with little in the way of revenue or cash, Celldex Therapeutics (NASDAQ:CLDX) boomed by around 647% as it worked on a trio of immunotherapies being developed in phase 1 clinical trials. One trial for chronic inducible urticaria dosed its first patient in December, and another trial should report preliminary safety data early next year.

In this case, the stock's strength seems to be a result of Celldex advancing its trials and experiencing little in the way of bad news. Keep an eye on the next data readouts to see if its programs are going to proceed to testing for efficacy in 2021. 

5. Retractable Technologies

If you're racing to get in on the gains of something like a coronavirus vaccine, it often pays to sell shovels. That's how Retractable Technologies (NYSEMKT:RVP) exploded by more than 676% this year -- selling syringes in anticipation of widespread vaccination. In the U.S. market, its revenue increased by 182.3% year over year in the third quarter, thanks to purchasing activity by the government.

It's also profitable, nearly debt-free, and growing its quarterly earnings at a blistering pace. What's not to like?

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.