Scientists are beginning to better understand how vaping increases the ability of COVID-19 to spread and cause severe symptoms, The New York Times reports.

Several studies have found that smoking regular cigarettes can more than double the risk of severe symptoms of COVID-19, but less is known about the relationship between e-cigarettes and the virus.

Vaping appears to make the lungs more vulnerable to bacteria and viruses, according to several studies in mice. Some research suggests that the coronavirus may have an easier time infiltrating the bodies of people who vape or smoke.

One recent study found young adults who vape are five times more likely to be diagnosed with coronavirus. One of the authors of that study, Bonnie Halpern-Felsher, said the link between vaping and the virus may involve more than biology. She noted people who vape often share spaces and equipment with other people. “And if you’re smoking or vaping, you’re not wearing a mask,” she said.