Popular lore is that Chinese pharmacist Hon Lik invented e-cigarettes in 2003 to help people quit smoking. The Times of London reported that it didn’t work for him.
Instead of “switching completely” he is a dual user, vaping and smoking at the same time.
Hon Lik’s experience is what you would expect from the strong and consistent epidemiological evidence that e-cigarettes keep people smoking cigarettes.
Incidentally, Hon Lik was not the first person to develop a working e-cigarette. Philip Morris had developed a functioning e-cigarette by the mid-1990s as part of its effort to hold on to customers who might otherwise quit. And, as both Hon Lik and the overall population experience shows, e-cigarettes are they are doing just that.
(The Times of London story, “England is an outlier in promoting vaping as a safe alternative to smoking. Other countries are far from convinced,” is worth reading.)