As the number of cases and deaths continues to increase in China and around the world, Cambridge, Massachusetts-based Moderna shipped its first batch of mRNA-1273, a vaccine against the virus, for a planned Phase I clinical trial in the U.S.

The experimental vaccine has been sent to the U.S. National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH) for the study. mRNA-1273 is a mRNA vaccine that encodes for a prefusion stabilized form of the Spike (S) protein. It was chosen by Moderna researchers in collaboration with scientists at the NIAID Vaccine Research Center (VRC). Funding for the manufacture of the batch came from the Coalition for Epidemic Preparedness Innovations (CEPI).

The S protein complex is part of the virus necessary for membrane fusion and host cell infection. This particular protein complex has also been the target of vaccines against the coronaviruses that cause SARS and MERS.

“I want to thank the entire Moderna team for their extraordinary effort in responding to this global health emergency with record speed,” said Juan Andres, Moderna’s chief technical operations and quality officer. “The collaboration across Moderna, with NIAID, and with CEPI has allowed us to deliver a clinical batch in 42 days from sequence identification. This would not have been possible without our Norwood manufacturing site, which uses leading-edge technology to enable flexible operations and ensure high quality standards are met for clinical-grade material.”

The Norwood facility manufactures the company’s mRNA development candidates, both vaccines and therapeutics. It has manufactured and released more than 100 batches from this site for human clinical trials. mRNA-1273 is a component of the company’s core prophylactic vaccines modality, which to date has had six positive Phase I clinical readouts across six different vaccines over the last four years.

The NIAID-Moderna clinical trial is planned to begin as early as April, which will be evaluated on a few dozen healthy patients to determine safety and immune response.

The World Health Organization is still not calling the coronavirus outbreak that causes COVID-19 a pandemic, even though there are new outbreaks in Iran, Italy and South Korea. There are some signs the outbreak is slowing in China, although new cases in South Korea, Iran and Italy are worrisome. As of Monday morning, South Korea reported 763 cases, Iran reported 43 cases, including eight deaths, and Italy reported an additional 48 cases bringing the country’s total to 124.

One definition of a pandemic is when a disease is being diagnosed on multiple continents. By that broad definition, COVID-19 is a pandemic. However, technical definitions evaluate whether the outbreaks are out of control and incurring significant damage.

The last named pandemic was in 2009, with the H1N1 flu virus that sickened more than 60 million people in the U.S. alone and killed almost half a million people worldwide.

“Does this virus [that causes COVID-19] have pandemic potential?” said WHO Director General Tedros Adhanom Ghebreyesus at a news conference in Geneva, Switzerland. “Absolutely it has. Are we there yet? From our assessment, not yet.”

As of today, more than 2,600 cases of COVID-19 have been reported outside of mainland China, where there have been more than 80,000 confirmed cases. The coronavirus has been confirmed in more than 35 countries.

“There looks to be sustained community transmission [outside China],” Raina MacIntyre, head of the University of New South Wales’s Biosecurity Research Program, told TIME.

David Heymann, a professor of Infectious Disease Epidemiology at the London School of Hygiene, told TIME, “The big problem is that the transmissibility of this virus is still not understood. It’s understood how it passes from person to person—social contact, a sneeze, a cough, face-to-face, and in hospital settings where there is not adequate infection prevention and control—but how easily this spreads in other circumstances is not known at present.”