San Francisco’s ban on sales of e-cigarettes could set back the war on smoking, according to public health experts in the UK who are doing everything they can to promote vaping as a way to quit.

As shopkeepers in San Francisco contemplate having to clear their shelves of vaping devices before the new year after a vote by city supervisors, many in the NHS are looking at ways to encourage more smokers to try them. This week in the north-east of England, an NHS taskforce urged doctors and nurses to talk to patients about smoking and reassure them vaping is safer.

The transatlantic divide over e-cigarettes is profound, rooted in social and ideological differences. San Francisco’s decision is directly in the tradition of Nancy Reagan’s admonition to young people offered drugs: “Just say no.” She first used the phrase in 1982 at a school in Oakland, across the bay from the city that is now saying no to vaping.

Public Health England has led the world in the opposite direction, backing harm reduction. An evidence review in 2015 concluded e-cigarettes were 95% less harmful than tobacco.

Martin Dockrell, the head of tobacco control at PHE, said there was a spectrum of opinion in the UK and US on e-cigarettes. San Francisco was very much “at one end of the spectrum – the abstinence-only, prohibition-style approach”, he said. While abstinence-only is the dominant view in tobacco control, “they also apply that to nicotine replacement therapy but also to e-cigarettes”.

There is huge concern in the US that young people who do not smoke will take up vaping. The Food and Drug Administration (FDA) and the federal government had recognised e-cigarettes could play an “off-ramp” role in helping smokers quit, but are concerned about the “on-ramp”, said Dockrell.

“In San Francisco, they have just abandoned any thought that e-cigarettes might be a significant off-ramp and they are only concerned about young people starting to use nicotine,” he said.

“Interestingly, they haven’t banned vaping cannabis. It’s still legal to vape cannabis and worse still, to smoke cannabis. It’s clear that the harm from smoking anything is much greater.

“Alcohol, smoked tobacco, cannabis, smoking or vaping – all of them are legal but the least harmful is e-cigarettes and they’ve banned them. Not just sales to young people, which we’ve done in this country, but for adults too. That is particularly difficult to understand.”

In February, PHE published an update of its evidence review which lamented the fact that only 4% of people trying to quit had used e-cigarettes.

Prof John Newton, its health improvement director, said: “We could accelerate the decline in smoking if more smokers switched completely to vaping.

“Recent new evidence clearly shows using an e-cigarette with stop smoking service support can double your chances of quitting.

“But with e-cigarettes currently used so rarely in services, it’s time for change. Every stop smoking service must start talking much more about the potential of vaping to help smokers quit.”

Across the Atlantic, there is great anxiety that non-smokers and particularly young people will take up vaping. There is concern that the flavourings could attract children and there has been a major outcry over the arrival of Juul, an attractively designed device resembling a USB stick that children have been using in schools. Juul was created in San Francisco and now has more than a 50% share of the US market.

The FDA has taken a tough line, mounting undercover operations and warning and fining retailers selling Juul and other devices to minors, as well as demanding Juul hand over documents on the science behind its devices and marketing strategy.

Speaking in April, Scott Gottlieb, the then FDA head, said: “In some cases, our kids are trying these products and liking them without even knowing they contain nicotine. And that’s a problem, because as we know, the nicotine in these products can rewire an adolescent’s brain, leading to years of addiction.

“For this reason, the FDA must – and will – move quickly to reverse these disturbing trends, and, in particular, address the surging youth uptake of Juul and other products.”

But in the UK, PHE says there is no evidence of a big surge in non-smoking young people vaping. Only 1.7% of under-18s use e-cigarettes weekly or more,a review in February found, and the vast majority of those also smoke. Among young people who have never smoked, only 0.2% use e-cigarettes regularly.

This month, a YouGov survey in England, Scotland and Wales published by Action on Smoking and Health found: “Young people vape mainly just to give it a try (52%) not because they think it looks cool (1%).”

Almost 77% of 11- to 18-year-olds had never tried it. Slightly fewer said they had tried vaping in 2019 than in the previous year (15.4% compared with 16%), although that was an increase from 12.7% in 2015.

A major driver of the hostility to vaping in the US is the involvement of tobacco companies. British American Tobacco, Altria (the parent company of Philip Morris), Imperial and Japan Tobacco have all diversified into e-cigarettes.

Anti-tobacco campaigners in the US spent decades fighting the wiles of the tobacco industry, gradually shutting down promotion of cigarettes and cementing the pariah status of the manufacturers. They refuse to believe e-cigarettes are anything more than a stalking horse to rehabilitate the industry.