This is new to me, so thought I'd share.  It's a big study, over several years, by University College London:
E-cigarette use for quitting smoking associated with improved success rates -- ScienceDaily
	
		
			
		
		
	
			
			E-cigarette use for quitting smoking associated with improved success rates -- ScienceDaily
 
				
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		