Research

Of all the coronavirus’s qualities, perhaps the most surprising has been that seemingly healthy people can spread it to others. This trait has made the virus difficult to contain, and continues to challenge efforts to identify and isolate infected people.

Scientists are beginning to untangle one of the most complex biological mysteries of the coronavirus pandemic: Why do some people get severely sick, whereas others quickly recover?

An experimental coronavirus vaccine developed by Johnson & Johnson protected monkeys from infection in a new study. It is the second vaccine candidate to show promising results in monkeys this week.

The company recently began a clinical trial in Europe and the United States to test its vaccine in people. It is one of more than 30 human trials for coronavirus vaccines underway across the world. But until these trials are complete — which will probably take several months — the monkey data offers the best clues to whether the vaccines will work.