Clinical data suggest that the immune system plays a part in the decline and death of people infected with the new coronavirus, and this has spurred a push for treatments such as steroids that rein in that immune response. But some of these treatments act broadly to suppress the immune system, stoking fears that they could actually hamper the body’s ability to keep the viral infection in check.

“My greatest fear is that this gets taken to an extreme, where people are using whatever they can get their hands on to turn off the immune response,” says Daniel Chen, an immunologist and chief medical officer at IGM Biosciences in Mountain View, California. “You can’t knock down the immune system at a time when it’s battling an infection.”…

In the absence of an answer, Ahmed is hopeful that researchers will arrive at a combination therapy, such as an IL-6 inhibitor that does not completely suppress the immune system, combined with an antiviral drug that directly targets the virus. Other drugs that target the immune system are also being tested, including one called anakinra, which targets a signalling protein called IL-1, and may provide a way to reduce specific immune responses without hampering CD4 and CD8 T cells, says Chen.

But Baillie says that given the widespread use of steroids to treat people with coronavirus already, it is important to collect data on the practice.