"The vaccine candidate that was given the first injections for the first person took place today," Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID), told reporters at a White House briefing on Monday.

The trial has begun at Kaiser Permanente Washington Health Research Institute (KPWHRI) in Seattle, and is funded by the NIAID, part of the National Institutes of Health (NIH).

The open-label trial enrolling 45 healthy adult volunteers aged 18-55 got its first participant receiving the investigational vaccine Monday, according to an NIH statement.

The study is evaluating different doses of the experimental vaccine for its safety and ability to induce an immune response in participants. This is the first of multiple steps in the clinical trial process to evaluate the potential benefit of the vaccine.

"This Phase 1 study, launched in record speed, is an important first step" toward achieving the goal of finding a safe and effective vaccine to prevent COVID-19 infection, Fauci said.

Study participants will receive two doses of the vaccine, which does not contain the virus itself, via intramuscular injection in the upper arm approximately 28 days apart, according to NIH.

Participants will be asked to return to the clinic for follow-up visits between vaccinations and be followed across the span of a year after the second shot, said Fauci.

Lisa Jackson, senior investigator at KPWHRI, who led the Phase 1 trial, said this work is critical to national efforts to respond to the threat of this emerging virus.

The vaccine is called mRNA-1273 and was developed by NIAID scientists and their collaborators at the biotechnology company Moderna, Inc., based in Cambridge, Massachusetts.

Dozens of research groups around the world are racing to create a vaccine as COVID-19 cases continue to grow.

Peter Hotez, professor and dean of the National School of Tropical Medicine at Baylor College of Medicine (BCM) in Houston, Texas, told Xinhua his group at the Texas Children's Hospital Center for Vaccine Development at BCM is working to develop a vaccine in collaboration with other U.S. institutions such as the University of Texas Medical Branch, and the New York Blood Center, and with the Virology Center at Fudan University in Shanghai, China.

"This is a great collaboration," Hotez said in an interview with Xinhua. "But vaccine development is not a fast process, and it's not clear whether we would have a vaccine ready to use before this current epidemic ends."

According to Fauci, even if initial safety tests go well, it may take about a year to 18 months before any vaccine could be ready for public use.

The number of COVID-19 cases in the United States topped 4,645 as of Monday afternoon, according to the Center for Systems Science and Engineering at Johns Hopkins University.