Shipping regulations passed in December 2020 and poised to take effect in the near future will greatly restrict access to electronic cigarettes. Since the law was enacted, additional research has shown that smokers who switch to vaping have a good shot at giving up cigarettes, and maybe even nicotine, forever. Congress is hindering this important public health victory.
Buried deep in the December 2020 COVID relief bill was an odd provision that had nothing to do with helping Americans financially crippled by the pandemic: a regulation (p 5,139) prohibiting the U.S. Postal Service from shipping “electronic nicotine delivery devices”—e-cigarettes. The final rule, once implemented, won't prohibit all mail carriers from delivering tobacco alternatives, but it will raise the associated compliance costs. The result is that bigger vaping supply companies will pass the added expense on to their customers, and smaller firms will just go out of business. 
The implication of such a rule was immediately obvious to adult ex-smokers who quit tobacco with the help of e-cigarettes. As Cato Institute research fellow Trevor Burrus pointed out at the time:
We continue to impose ineffective and harmful restrictions on vaping. We’ll see more smokers as a result. Public health, which is supposed to be something we all care about a great deal these days, will suffer.
There was a decent body of evidence in December indicating that vaping is relatively safe and can help smokers give up cigarettes. In the almost five months that have passed since the legislation was enacted, several systematic reviews and studies investigating the smoking-cessation effects of vaping have been published. Our understanding of electronic cigarettes remains limited, but research continues to show that the tobacco alternatives can help smokers reduce or eliminate their cigarette consumption, a clear victory for public health.
First up, an April 2021 systematic review from the highly respected Cochrane Collaboration. The researchers surveyed 56 completed studies, representing 12,804 participants. They only included studies that reported six months of cigarette abstinence or longer and data on adverse events related to vaping at one week or longer. They cautioned that their results were “limited mainly by imprecision due to the small number of RCTs [randomized controlled trials], often with low event rates,” but they nonetheless concluded:
There is moderate-certainty evidence that Ecs [electronic cigarettes] with nicotine increase quit rates compared to ECs without nicotine and compared to NRT [nicotine replacement therapy]. Evidence comparing nicotine EC with usual care/no treatment also suggests benefit, but is less certain … Confidence intervals were for the most part wide for data on AEs [adverse events], SAEs [serious adverse events] and other safety markers, though evidence indicated no difference in AEs between nicotine and non-nicotine ECs.
Cochrane classifies this as a “living review” and will publish updates as new evidence becomes available. While we wait on them, a March review offers some additional data worth considering. The researchers reviewed seven clinical trials that assigned participants to use nicotine-containing e-cigarettes, approved nicotine patches and gums, or a placebo-like nicotine-free e-cigarettes or usual care. While warning about the risk of bias and moderate heterogeneity in the studies (which makes combining their results difficult), the researchers reported that
Smokers assigned to use nicotine e-cigarettes were more likely to remain abstinent from smoking than those assigned to use licensed NRT [nicotine replacement therapy], and both were more effective than usual care or placebo conditions.
What's going on here?
Two recent studies may explain why vaping helps turn smokers into ex-smokers. The results of these papers point to the widespread availability of electronic cigarettes and e-liquids and how the devices deliver nicotine as the primary reasons many people can give up smoking. A survey of just over 1,000 people conducted in New Zealand, for example, found that flavor diversity strongly influenced dual users of cigarettes and e-cigarettes and ex-smokers to take up vaping in the first place. Access to e-liquid flavors remained an important reason why all groups in the survey continued vaping.
The researchers rightly warned that “extravagant marketing” of flavored vape products could entice non-smokers to take up vaping. But this could be easily addressed if the FDA would allow e-cigarette makers to market their products as smoking cessation devices. Nothing says “uncool” like a commercial urging your boomer parents to quit smoking with “electronic nicotine delivery systems.” But the FDA does not allow e-cigarettes to be advertised this way for now.
Beyond widespread device and liquid availability, a recent survey of 76 users of JUUL e-cigarettes (many of whom were ex-smokers) suggested another reason why vaping may aid smoking cessation. Depending on the device, it could be a more efficient nicotine-delivery method than smoking.  The study's primary conclusion: "On average, JUUL users reported low to medium nicotine dependence ... JUUL user dependence may be more similar to e-cig user dependence than cigarette smoker dependence. The authors' speculation about why this is was striking:
[Because the devices don't burn out] e-cig users learn to take puffs intermittently but less frequently over much longer periods, avoiding the high peaks and troughs in blood nicotine levels that characterize cigarette smoking. It is possible that this different pattern of nicotine absorption with e-cigs leads to lower levels of perceived dependence even with a device capable of delivering nicotine like a cigarette if used like a cigarette.
If that analysis is correct, and previous research suggests it is, it means that vaping is not only safer than smoking but may actually decrease nicotine dependence, making efforts to restrict access to e-cigarettes all the more misguided.
 The authors also reported that "Many JUUL users in this study were past other tobacco users, with the majority of these users being former cigarette smokers (78% of the sample). More than two-thirds of former smokers in this sample reported quitting smoking after initiating e-cig use ..."