As Covid-19 Vaccine Development Pushes Ahead, Researchers Probe Safety

In 2017, researchers found that some children who got a new vaccine against the tropical disease dengue later came down with a severe case of the illness, forcing production to temporarily stop. Now, researchers developing coronavirus vaccines aim to avoid a similar fate that could set back fast-moving efforts to curb the pandemic.

The researchers say they have designed Covid-19 vaccines in ways that aim to make sure they fight off infections, rather than worsen them.