<span style="color: #222222;">The first human trial to evaluate a candidate vaccine against coronavirus disease 2019 has begun in Seattle, US health officials said. <br />''<br />''The US National Institutes of Health (NIH) said in a statement that the open-label trial will enroll 45 healthy adult volunteers ages 18 to 55 years over approximately 6 weeks. The first participant received the investigational vaccine yesterday.</span><br />