Medical teams from across China began leaving Wuhan this week, after infections there have dropped.Credit: STR/AFP/Getty

• The first human clinical trial for a potential coronavirus vaccine, developed by the drug company Moderna, started in the United States this week. Inovio Pharmaceuticals plans to begin similar safety trials for its SARS-CoV-2 vaccine in April. These are the five key questions vaccine researchers will be trying to answer about people’s immune response to the virus and how to ensure any vaccine is safe and effective. (Nature | 6 minutes)

• More people have now died of COVID-19 outside China than inside the country. The total number of new infections being reported each day in the rest of the world is also greater than those in China. (Nature | Continuously updated)

• The US government’s crackdown on scientists who do not disclose the research that they conduct in China prompted chemist Weihong Tan to leave the University of Florida. Now at Hunan University in south-central China, Tan says he has co-developed a quick coronavirus test that produces results in 40 minutes. (ProPublica | 28 min read)

• The risk of severe illness and death from COVID-19 is highest in older people, but young adults are not out of the woods. The US Centers for Disease Control and Prevention says that up to one-fifth of infected people aged 20–44 have been ill enough to be hospitalized; 2-4% of these required treatment in an intensive-care unit. No intensive-care admissions or deaths were reported among people younger than 20. (STAT | 7 min read)

Read the latest coronavirus news, continuously updated on Nature.