Although more than one-third of Americans are fully vaccinated against the coronavirus, millions of people still have not received a single dose.

Reasons for not getting a shot vary — some don’t want one, while others say they’ll wait a bit longer to decide. And then there are people who want to get vaccinated but are in areas so remote that they can’t easily get to a typical vaccination site.

They include people working on oil rigs in the Gulf of Mexico or living in rural areas far from the nearest doctor’s office or pharmacy. Drone companies are positioning themselves to deliver refrigerated medical products to those people. If the plans don’t pan out in time to combat the coronavirus crisis, then they hope to be set up to assist swiftly in the world’s next big health scare.

Draganfly, based in Saskatoon, Canada, and San Francisco-based Volansi are among the firms operating drones in the United States right now with medical delivery partnerships.

Draganfly has been around since the 1990s and will begin test flights with coronavirus vaccines in Texas next month with Coldchain Technology Services, a health-care supply chain management company. Volansi, founded in 2015, has been running drones carrying other refrigerated medicines and vaccines with Merck in North Carolina since October.

Drones tend to be faster and cheaper for handling smaller payloads to remote locations than trucks or helicopters, said Wayne Williams, executive director of Coldchain, which is headquartered in Spring Branch, Tex.

“If I have to get a lifesaving vaccine to somewhere that’s about [300 miles] from here, I have to find a courier, get them on the road, and it can take up to seven hours to get it delivered. If I put the package on a drone, I’m still able to track it, and it gets there sooner for a lot less money,” Williams said.

Last week, Coldchain announced plans to spend $750,000 on Draganfly’s equipment to ship medical supplies and coronavirus vaccines on an experimental basis to nearby locations.

Unmanned aerial vehicles are shaping up to assist during the pandemic in other ways, too. Draganfly developed a system that can measure people’s vital signs such as heart rate and blood pressure from a drone. Drones from the Chinese manufacturer DJI have been used to monitor social distancing in Elizabeth, N.J., over the past year. Meanwhile, more than a few firms have announced disinfecting drones to spray potentially contaminated zones from above.

Drones aren’t transporting coronavirus vaccines in the United States yet. But Coldchain wants to change that.

The company will work with the Federal Aviation Administration this summer to obtain approval for delivery routes in Texas. This comes after the FAA issued new drone rules in December in a step toward enabling widespread commercial deliveries. Phase two for Coldchain will be to fly the drones farther, out of their line of sight, to trained emergency medical services workers.

Coldchain has already developed 12-inch cube-shaped thermal containers to be carried by Draganfly’s drones.

The company’s temperature-controlled boxes can hold about 600 to 1,500 vials of vaccines, depending on the provider. And they were constructed to maintain the super-low temperatures required by Pfizer for 48 hours, and Moderna for at least 72 hours, Williams said. Johnson & Johnson’s one-dose vaccine can be kept at slightly higher temperatures, between 36 and 46 degrees Fahrenheit, which the containers can maintain for about 96 hours, Williams added.

The packages have data collection devices that will alert Coldchain to variations in vaccine temperatures, the company says. Once the drone makes it to a drop-off site, the recipients can use a smartphone code outside the container to determine the payload’s internal temperature.

Draganfly offers a variety of drones customized for specific jobs across education, law enforcement and agriculture. Coldchain says it plans to start vaccine deliveries in Texas with the firm’s medium-range drones capable of flying about 372 miles round-trip on a charge.

Draganfly is not the only start-up transporting medical supplies in the United States amid the pandemic. In October, Volsani, based in Concord, Calif., began its commercial health-care flights around Wilson, N.C., where the company distributes pneumonia and hepatitis vaccines in partnership with the pharmaceutical giant Merck.

Volansi hasn’t transported coronavirus vaccines, although “our payload boxes are designed specifically to carry covid-vaccine types,” said Hannan Parvizian, the company’s chief executive.

Germany’s Wingcopter is also racing to distribute coronavirus vaccines, while San Francisco’s Zipline started dropping off Oxford-AstraZeneca vaccines in Ghana earlier this year. Walmart partnered with Zipline in September for on-demand medical supply delivery.

Draganfly says what makes its plan with Coldchain different is that it has coronavirus vaccine customers ready to receive deliveries if testing pans out this summer.

Even if coronavirus vaccine delivery takes off in the United States, the small air vehicles would help only so much. More than 37 percent of Americans already are vaccinated, and studies have shown that about a quarter of people who haven’t had a shot don’t want to get vaccinated at all. It’s also late in the pandemic. The Centers for Disease Control and Prevention has eased its guidance on wearing face masks indoors, and cities nationwide have dropped other pandemic-related restrictions.

Drone companies say they’re laying the groundwork now so that they can work more swiftly during future health crises.

“This won’t be the last vaccine that needs to be distributed,” said Cameron Chell, chief executive of Draganfly. “But next time as a society, we’re going to respond much quicker.”