Don Humbertson, a 64 year old lung cancer surviver, is examined by Dr. Wade Harvey at the Clay-Battelle Community Health Center March 21, 2017 in Blacksville, West Virginia.

Companies that sell short-term health plans got a boost Wednesday after the Trump administration issued a final rule that loosened restrictions on plans that don't comply with the Affordable Care Act.

The new rule allows consumers to enroll in short-term coverage for up to 36 months, instead of just 3 months allowed under the ACA rules set up under former President Barack Obama, more commonly known as Obamacare.

Shares of the companies that sell the plans jumped after the rule was released.

Health Insurance Innovations shares rose more than 13 percent in early afternoon trading, while eHealth shares were up more than 5 percent.

Short-term plans, which were designed to provide temporary care for people in between jobs, often come with substantially lower monthly premiums than other forms of insurance but tend to offer less coverage. They generally don't preexisting conditions or prescription drugs.

In an interview Wednesday with CNBC's "Squawk Box," Health and Human Services Secretary Alex Azar said the new rules could provide relief to part-time or contract workers or people in rural areas that can't afford a traditional ACA plan.

"We believe in options," Azar said. "This is instead giving many millions of Americans an additional option."

—CNBC's Bertha Coombs contributed to this report.