Laboratory technicians work on testing samples from people to be tested for the COVID-19 coronavirus at a laboratory in Shenyang in China's northeastern Liaoning province on February 12, 2020.

Human trials for a potential vaccine to prevent COVID-19 could begin "within a few weeks" with a vaccine ready for public use within the next 12 to 18 months, a top U.S. health official said Thursday.

"We said ... that it would take two to three months to have it in the first human," Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told the House Oversight and Reform Committee on Thursday at a hearing on the nation's preparedness for the outbreak.

"I think we're going to do better than that," he said. "I would hope within a few weeks we may be able to make an announcement to you all that we've given the first shot to the first person."

The National Institutes of Health has been working with biotech company Moderna to develop a vaccine using the current strain of the coronavirus.

Fauci has said the potential vaccine contains genetic material called messenger RNA, or mRNA, that was produced in a lab. The mRNA is a genetic code that tells cells how to make a protein and was found in the outer coat of the new coronavirus, according to researchers at the Kaiser Permanente Washington Health Research Institute.

The mRNA instructs the body's own cellular mechanisms for making proteins to make those that mimic the virus proteins, thereby producing an immune response.

"I want to make sure people understand, and I've said that over and over again, that does not mean we have a vaccine that we can use," Fauci cautioned. "We mean it's record time to get it tested. It's going to take a year to a year and a half to really know if it works."