(Bloomberg) -- The U.S. Food and Drug Administration modified its stance on Covid-19 and vaping, saying it has an unknown effect on the risk of the new coronavirus, while warning that smoking can create worse outcomes.

“E-cigarette use can expose the lungs to toxic chemicals, but whether those exposures increase the risk of Covid-19 is not known,” the agency said Wednesday in an emailed response to a question from Bloomberg News.

The agency had said late last month that vapers and smokers with underlying health conditions might be at higher risk from complications.

Its description of cigarettes’ risks also differed from its earlier statements. “Cigarette smoking causes heart and lung diseases, suppresses the immune system, and increases the risk of respiratory infections,” FDA spokeswoman Alison Hunt said. “People who smoke cigarettes may be at increased risk from Covid-19, and may have worse outcomes from Covid-19.”

The new statement comes as the disease afflicts young people in some countries at rates that are surprising, given initial data out of China, and some health experts speculate as to whether vaping could play a role.

Other U.S. agencies have issued mixed warnings on both smoking and vaping. Nora Volkow, director of the National Institute on Drug Abuse, wrote a recent blog post warning that the coronavirus “could be an especially serious threat to those who smoke tobacco or marijuana or who vape.”

Michael R. Bloomberg has campaigned and given money in support of a ban on flavored e-cigarettes and tobacco. He is the majority owner of Bloomberg LP, the parent company of Bloomberg News.

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