²ÝÁñÉçÇø

Back in the 1980s, scientists in the U.K. performed an experiment that — at first glance — sounds unethical. "Volunteers came into the lab and someone squirted virus up their nose," says computational biologist Jennie Lavine.

The researchers took a liquid packed with coronavirus particles and intentionally tried to make 15 volunteers sick.

Ten people got infected. The other five fought off the virus, says , who's now at the  but was at Emory University when she spoke to NPR.