Data from dozens of UK health-care workers suggest a tantalizing possibility: that some people can clear a nascent SARS-CoV-2 infection from their bodies so quickly that they never test positive for the virus nor even produce antibodies against it1. The data also suggest that such resistance is conferred by immune players called memory T cells — possibly those produced after exposure to coronaviruses that cause the common cold.

“I’ve never seen anything like that. It’s really surprising that the T cells might be able to control an infection so quickly,” says Shane Crotty, an immunologist at La Jolla Institute for Immunology in California, who was not involved in the research.

But the study’s authors strongly caution that their results do not show that people who have had the common cold are protected against COVID-19. And the authors also acknowledge that their findings have many caveats, meaning that it’s too early to say with certainty that people can stop an infection in its tracks.