CHICAGO (AP) - A study of U.S. poison center calls has found that e-cigarettes are sickening more and more children under 6.

The research in Monday's journal Pediatrics says about 14 children per month were sickened by e-cigarettes when the study began in January 2012, and it rose to about 223 per month by the time the study ended in April 2015.

Researchers say most kids weren't seriously harmed, but one child died and several others had severe complications including comas and seizures.

Lead researcher Dr. Gary Smith says, "This is an epidemic by any definition." Smith is the director of the Center for Injury Research and Policy at Nationwide Children's Hospital in Columbus, Ohio.

Researchers say the study shows that parents need to do a better job of keeping e-cigarettes out of their children's reach.