Surgeon General Vivek Murthy tossed a bone to the puritanical ideologues of the anti-smoking movement this week with a warning that the rise in vaping by young people is “a major public health concern.”

“Any tobacco use, including e-cigarettes, is a health threat,” Dr. Murthy insisted, “particularly to young people.”

Now, look: Smoking tobacco, especially cigarettes, is really, really bad for you. Even if the habit doesn’t give you cancer, the longterm health effects are serious — for your lungs, your heart and more.

But scientists are only beginning to study the health impact of e-cigs, as Murthy admitted. And the odds they’ll find serious ones are low, since the vapor has virtually none of the secondary chemicals and particles that make actual smoke so harmful.

Yet, for whatever reason, the anti-smoking movement has turned obsessively against any thought of harm reduction: Vaping is merely the latest alternative to cigarettes to be denounced as a “gateway” to the real thing.

This, when — as Jacob Sullum noted in Forbes in September — US teens’ smoking rates “have fallen to record lows even as more and more of them experiment with vaping.”

E-cigs may yet prove a fad, or perhaps they’ll someday eclipse real cigarettes — by replacing them, which would be a huge net gain for public health.

Assuming the absolutist ideologues don’t manage to crush a promising alternative in its infancy.