Four adults, the first of 45 eventual participants, received their first doses of an experimental vaccine developed through a partnership between the US National Institute of Allergy and Infectious Diseases (NIAID) and Moderna, a biotechnology company based in Cambridge, Massachusetts. But although it is an important milestone, the phase I trial is just the beginning of a long process to test the drug’s safety and efficacy.

The trial is being conducted at Kaiser Permanent Washington Health Research Institute, and will test a range of doses of the vaccine. Over the next 6 weeks, participants will receive their first doses, followed by a second 28 days later. Follow-up visits both in person and over the phone will assess participants’ health over a 14-month period, and blood samples will help researchers evaluate the body’s immune response to the experimental vaccine.