Exclusively using (or “vaping”) e-cigarettes can help people quit smoking, but many people using e-cigarettes to quit smoking continue to smoke cigarettes. New research led by investigators at Massachusetts General Hospital (MGH) reveals that respiratory symptoms—such as cough and wheeze—are more likely to develop when people use both e-cigarettes and tobacco cigarettes together compared with using either one alone. The findings are published in the American Journal of Respiratory and Critical Care Medicine.