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It’s a controversial idea: Intentionally infect people with the virus that causes Covid-19 to test the effectiveness of a potential vaccine. The approach is called a human challenge trial, and it’s not the usual way a vaccine is tested. More commonly, researchers track thousands of people, some of whom receive a vaccine, and others a placebo, and then see who becomes infected in the natural course of their lives. It’s a slower process, but poses fewer risks than deliberately infecting people after they’ve received a vaccine. (Reddy, 5/11)

The World Health Organization chief said Monday there are around seven or eight “top” candidates for a vaccine to combat the novel coronavirus and work on them is being accelerated. WHO Director-General Tedros Adhanom Ghebreyesus told a U.N. Economic and Social Council video briefing the original thinking two months ago was that it may take 12 to 18 months for a vaccine. But he said an accelerated effort is under way, helped by 7.4 billion euros ($8 billion) pledged a week ago by leaders from 40 countries, organizations and banks for research, treatment and testing. (Lederer, 5/11)

Johnson & Johnson’s race to manufacture a billion doses of coronavirus vaccine is ramping up in a small biotechnology plant near Interstate 95 in Baltimore. But even as technicians prepare to lower 1,000-liter plastic bags of ingredients into steel tanks for brewing the first batches of experimental vaccine, international concern is bubbling about what countries will get the first inoculations. The Baltimore plant is the second of four planned locations around the world where Johnson & Johnson plans to pump out vaccine on a massive scale, months before testing the first dose in a human being. (Rowland, Johnson and Wan, 5/11)

Moderna is moving at unprecedented speed to develop a vaccine to prevent infection from the novel coronavirus. But the biotech’s soaring stock price is moving faster, which raises an important question: Are investors taking on too much risk?Since late February, Moderna shares have more than tripled in value — making it one of the top-performing biotech stocks this year. On Monday, shares hit an all-time high of $66. (Feuerstein, 5/12)

Five years ago, Bill Gates warned that the biggest potential killer the world faced wasn’t war, but a pandemic. The billionaire spent hundreds of millions of dollars to find faster ways to develop vaccines and create disease-tracking systems. He urged world leaders to build national defenses against new infectious diseases. Looking back, Mr. Gates said, “I wish I had done more to call attention to the danger.” The Microsoft Corp. co-founder is now squaring off against the scenario he sought to forestall. “I feel terrible,” he said in an interview. “The whole point of talking about it was that we could take action and minimize the damage.” (McKay, 5/11)