Medical Examiner

Does Smoking Make COVID-19 Worse? Better? Here’s What We Actually Know.

The research on the relationship is all extremely preliminary and should change little of how we think about cigarettes or vaping.

A single burned cigarette on a backdrop of coronavirus cells
Photo illustration by Slate. Images via Prakasit Khuansuwan/EyeEm via Getty Images Plus and Elena Mozhvilo/Unsplash.

Are smokers and vapers more likely to die of COVID-19? To judge by news coverage of the topic, the answer is an unequivocal yes. The New York Times, Wired, CNN, Bloomberg, and numerous other publications have run stories warning that smokers and vapers are at higher risk. Anti-tobacco groups are using the pandemic as an opportunity to push for new restrictions on nicotine, ranging from bans on vapor products to the complete prohibition of cigarettes. At least one senator, Richard Blumenthal of Connecticut, is citing the disease as justification for a national ban on flavored e-cigarettes, while House Democrats are urging the FDA to temporarily ban e-cigarettes entirely. Amid all this alarm, one complication has received relatively little notice: Emerging evidence on the risk factors for COVID-19 is ambiguous with regard to smoking and virtually nonexistent for its relationship to vaping.

Few would doubt that, absent compelling evidence to the contrary, smoking is a plausible risk factor for COVID-19. Smoking is known to generally suppress the immune system’s capacity to fight infection, and one would expect smokers to be particularly susceptible to a novel respiratory disease. An evidence review published on March 20, drawing on studies that analyzed hospitalizations in China, concluded that the data, although limited, indicated that “smoking is most likely associated with the negative progression and adverse outcomes of COVID-19.” Smoking is also associated with other conditions that may worsen COVID-19 outcomes, including diabetes. Thus, initially there was a reasonable expectation that smoking may be a significant risk factor.

A month later, the picture is less clear. On April 3, scientists at the Centers for Disease Control and Prevention published an analysis of more than 7,000 COVID-19 cases in the United States, of which strikingly few consisted of smokers. Current smokers comprised only 1.3 percent of the cases and former smokers another 2.3 percent; by comparison, smokers make up about 14 percent of the general American population and about 8 percent of the population over 65. A more detailed multivariate analysis of more than 4,000 cases in New York, published as a pre-print by researchers at New York University on April 11, yielded similarly unexpected results: “Surprisingly, though some have speculated that high rates of smoking in China explained some of the morbidity in those patients, we did not find smoking status to be associated with hospitalization or critical illness.” A third study from a hospital in Paris found that current smokers were underrepresented in symptomatic and hospitalized cases. A fourth study from northern France, published as a pre-print on Thursday, also found smokers to be significantly less likely to test positive for infection. The authors note in the discussion section of the paper that the “protection associated with smoking in our study was very substantial (75% decrease in risk of infection), and deserves full attention.”

There’s a scene in the 1973 film Sleeper in which the protagonist, waking up 200 years in the future, is given a cigarette by a doctor who exhorts him: “It’s tobacco. It’s one of the healthiest things for your body.” A few people are taking the low prevalence of smokers among COVID-19 cases as evidence that that future has come to pass. David Hockney, an inveterate smoker and brilliant artist (though not, it should be noted, an epidemiologist), wrote the Daily Mail to suggest that smoking has a protective effect: “Could it not be that smokers have developed an immune system to this virus? With all these figures coming out, it’s beginning to look like that to me.”

So, time to break out the smokes? Well, not so fast. Given prior expectations about the effects of smoking on the immune system, it’s best to view the emerging data as intriguingly suggestive while keeping in mind the difficulty of conducting studies in the fog of a pandemic. Other researchers have cautioned that samples may be skewed by underreporting, and attempting to control for multiple variables is difficult; contradictory data could appear at any time. It’s also unclear by what mechanism smoking would reduce risk. Speculation has focused on interactions between nicotine and the ACE2 receptor, where the virus enters the body’s cells, but no one knows for sure what that implies for the progression of COVID-19 or modulation of the body’s immune response. (The Daily Mail article offers an unexpectedly detailed summary of the issue, though.) More evidence is needed before conclusions can be reached with certainty, but there’s enough ambiguity in the data to spur further investigation: Researchers in France are planning to test whether nicotine patches affect outcomes among patients and health care workers.

More to the point, smoking is a destructive habit regardless of its relationship to COVID-19. Sara Watle of the Norwegian Institute of Public Health, which recently removed smoking from its list of likely risk factors for COVID-19, is quick to add that “it is well established that smoking is unhealthy and contributes to serious health outcomes, so it is always a good idea to stop smoking!” Similarly, a pre-print by researchers in Greece and the United States concludes that although the interaction of smoking and the pandemic is currently unknown, “the generalized advice to quit smoking as a measure to improve health risk remains valid.” Regardless of how ongoing investigations into nicotine’s effects on COVID-19 turn out, they’re not going to overturn decades of research establishing smoking as extremely detrimental to health. Returning to the Mad Men–era ubiquity of smoking isn’t an advisable path toward fighting the virus. (If nicotine does turn out to provide some protective effect, ideally it will hold when delivered by means safer than inhaling carcinogenic smoke.)

The question of whether vaping increases the risks of COVID-19 has received nearly as much attention as the effects of smoking but has not, in fact, been specifically studied. Nonetheless, warnings that vaping will worsen the pandemic have been given substantial press and are lending further motivation to political efforts to ban e-cigarettes. These fears are highly speculative. The Food and Drug Administration initially joined other groups warning that vapers may be at higher risk, but a spokesperson for the agency revised its advice two weeks ago to acknowledge that the relationship is currently unknown. Similarly, an advisory from the American Cancer Society notes that there “is currently no evidence supporting a direct connection between e-cigarette use and getting COVID-19” and there is “very little direct evidence that e-cigarette use affects COVID-19 outcomes.”

Messaging on vaping is complicated by the fact that millions of vapers are former smokers. In a letter to the FDA signed by 13 experts in the field of tobacco harm reduction, the authors urge that any advice on vaping and COVID-19 should be “based on recognition of the pronounced difference in risk between smoking and vaping, the difficulty that many face in quitting nicotine use completely, the risks of harmful unintended consequences, and the strong association of smoking with poverty and various forms of disadvantage.” In other words, they worry that the promotion of unfounded fears in relation to COVID-19 may drive vapers back to smoking, with destructive consequences for their health.

Recent experience suggests that this concern is well founded. In a different outbreak, the mysterious lung illnesses that began last year and hospitalized nearly 3,000 Americans, statements by the CDC, campaigns by anti-smoking advocacy groups, and reports by mainstream press all blamed nicotine e-cigarettes for the disease. It was later established that contaminants in primarily black-market cannabis products were overwhelmingly behind the outbreak, but the damage was done: Public opinion turned decisively against e-cigarettes, flavor bans proliferated, and misperceptions about the risks of vaping have persisted in spite of the newer information.

Less than a year later, both the media and anti-smoking groups seem poised to repeat the mistake. It’s possible that vaping may marginally increase the risks of COVID-19; it’s also possible that exaggerating fears will harden public attitudes against vaping, discourage smokers from switching, and lead to even more restrictions on e-cigarette products. These possibilities highlight the danger of politicizing science and taking advantage of a frightening illness to promote a preexisting agenda. Policies put into place during a once-in-a-lifetime pandemic are unlikely to be accurately informed by long-run considerations, but their effects will last beyond the current crisis. Congressional Democrats’ request to ban e-cigarettes while leaving conventional cigarettes on the market, for example, was exceptionally ill-advised, and the FDA wisely declined to take action.

More research is clearly needed on the relationship between smoking, vaping, and COVID-19, but the findings probably shouldn’t much influence our opinions of those practices. Smoking remains detrimental to health, and vaping remains a viable off-ramp to quitting. Investigations into nicotine’s effects on the virus may well come to nothing. However, we also shouldn’t allow demonization of the drug to prevent us from being open to potentially useful discoveries. If the tobacco plant turns out to play a beneficial role in this pandemic after centuries of blame for so many ills, it will be yet another unexpected plot twist in an already very unusual year.