There has been a great deal of discussion in the news media about the potential relationship between COVID-19 and tobacco use, including smoking and vaping.  We address some of the most asked questions here.

Does smoking increase the likelihood of contracting COVID-19?

There isn’t yet direct evidence that a history of smoking makes an individual more likely to contract COVID-19, but there is epidemiological evidence that smoking increases the risk of viral lung and throat infections. The increased risk stems from the fact that smoking suppresses immune function and inflames the lungs and throat. Results from research that specifically examines smoker susceptibility to other coronaviruses such as SARS and MERS are mixed. This may be because healthcare workers, who have low smoking rates in recent years, are overrepresented among cases because many early transmissions occurred within hospital settings. Early evidence on COVID-19 susceptibility may be similarly confounded by occupation. One study that compared MERS patients to case controls, excluding anyone who might have contracted MERS in a healthcare setting, did find smoking to be a significant risk factor for infection.

Much of the speculation about this possible association in the news media is based on early studies from China indicating that men were contracting COVID-19 at higher rates than women. For example, Guan et al. found in a study of nearly 1100 hospitalized COVID-19 patients that 58 percent were men, and men smoke at a rate twenty times higher than women in China. However, Italy has lower total smoking prevalence than China and women’s smoking prevalence is much closer to men’s, and researchers have observed similar disparities by sex. Researchers continue to try to understand these differences and what they might be showing.

On a related note, though there is little research on this dynamic, the World Health Organization (WHO) notes on their website how often smokers touch their mouths with their fingers, which is known to be a risk factor for contracting COVID-19. This reinforces that we must wash our hands frequently with soap and not touch our faces. The WHO also highlights how hookah/waterpipe users often share their smoking device with others, thereby sharing bodily fluids, and that this sharing presents a risk factor for COVID-19. This is a compelling reason to cease waterpipe use.

What are smoking’s effects on COVID-19 outcomes?

The underlying logic of a smoking-to-COVID-19 relationship is that smoking is an established risk factor for respiratory infections, including influenza, because it undermines the immunological response that a person can otherwise mount against a viral infection. It is hypothesized that this is likely to also be the case with COVID-19. Furthermore, there is a very strong indirect relationship between smoking and the pre-existing conditions, including COPD and heart disease, that have emerged as risk factors for COVID-19 severity and death.

Not surprisingly, a recent meta-analysis of six studies in China—several of which have been cited frequently in the news media— finds that smoking is most likely associated with both negative progression and adverse outcomes in COVID-19 patients. Guan et al. (mentioned earlier) found that current and former smokers were more likely to have a severe outcome. Another study in the Chinese Medical Journal finds that smokers were more likely to be in the group of patients that deteriorated while hospitalized, but the sample was very small (11 out of a total of 78 patients deteriorated).

Currently, in the CDC’s web-based discussion of who is at higher risk for severe illness from COVID-19, under “Conditions that can cause a person to be immunocompromised,” the agency reports “cancer treatment, smoking, bone marrow or organ transplantation, immune deficiencies, poorly controlled HIV or AIDS, and prolonged use of corticosteroids and other immune weakening medications.” (emphasis added). Similarly, the WHO reports that “Conditions that increase oxygen needs or reduce the ability of the body to use it properly will put patients at higher risk of serious lung conditions such as pneumonia,” adding that “Smokers may also already have lung disease or reduced lung capacity which would greatly increase risk of serious illness.”

Does e-cigarette use (vaping) increase the likelihood of contracting COVID-19?

There is currently no evidence supporting a direct connection between e-cigarette use and contracting COVID-19.  This does not mean that there is no connection, instead it means that researchers have not yet identified one. Research is ongoing in this area, particularly in the US where the proportion of young people with severe cases of COVID-19 might be higher than in some other countries. One hypothesis for this difference is the higher prevalence of e-cigarette use by youth. Notably, however, researchers are also making strong connections between obesity and COVID-19, and in the US, obesity is higher than in most countries including among youth and young adults, so there are many complexities here that researchers do not yet understand.

Does e-cigarette use (vaping) affect COVID-19 outcomes?

There is currently little direct evidence that e-cigarette use affects individuals’ COVID-19 outcomes, and a small amount of indirect evidence. Some news outlets are reporting this linkage based on a general hypothesis that because there is emerging evidence that e-cigarette use causes lung damage, and the early evidence suggests that those with respiratory challenges fare less well with COVID-19, then those who use e-cigarettes are more likely to face worse outcomes. This logic is reasonable. There was also a recent small-sample study of mice that found that vaping mice were less likely to recover from influenza than non-vaping mice. It is possible that vaping impaired the mice’s immune responses though generalizability to either humans or to humans and COVID-19 is not clear. Accordingly, researchers are watching this dynamic very closely.

What about the effects of secondhand smoke/e-cigarette aerosol (“vapor”) and COVID-19?

It is vital to protect individuals from exposure to secondhand smoke and e-cigarette aerosol (“vapor”) in this time when we are all in close quarters with family and others. Those exposed to smoke are at elevated risk for developing cancer, heart disease and/or stroke, among other diseases. Exposed infants are at elevated risk of sudden infant death syndrome. Research also shows that secondhand aerosol from e-cigarettes contains toxicants and should be treated similarly to secondhand smoke in the home. Smokers and e-cigarette users need to go outside while also observing other recommended safe social distancing practices.

Is this global pandemic a good time to quit smoking?

Quitting smoking yields large and immediate benefits to your health, no matter the time. Perhaps these benefits are larger now than ever. While there isn’t yet direct evidence that quitting will help smokers avoid more severe consequences of COVID-19, we do know that, after quitting, there are rapid improvements in carbon monoxide levels and the function of respiratory tract cilia, and slightly slower improvements over time in immune function. Further, decreasing one’s movement in and out of buildings to protect loved ones from secondhand smoke exposure, also increases the effectiveness of social distancing. All these improvements should help decrease the risk and severity of COVID-19 infections.

There’s a second important dynamic, too: for some smokers, this crisis might provide inspiration or motivation, or a “teachable” moment for those who hadn’t thought much before about quitting. This might be the time that by reaching out to them about quitting in this time of COVID-19, they might be inspired or motivated to try.

It is important to note, too, that for some smokers, quitting under enormous stress might diminish the likelihood of successful cessation. People who choose not to quit shouldn’t be stigmatized. But we should do everything to help those who choose to quit to succeed. The likelihood of successful quitting is enhanced by using medications approved by the US Food and Drug Administration, including nicotine replacement therapies (NRTs, which include gum, lozenge, spray and patch), varenicline and bupropion, which work most effectively in combination with counseling. While getting a new prescription might be challenging at this time in many places, NRTs are available without prescription from local pharmacies in many countries. Many countries also have quit-lines and other services available free of charge to those trying to quit.

The US Centers for Disease Control have some excellent free resources to help smokers quit here. For US readers, the Truth Initiative has an evidence-based program to help youth stop vaping. Many governments provide similar services.

This is a fast-moving area of research and we will be updating our Tobacco Atlas readers as we learn more. We wish all of our readers the best in this challenging time.

By Jeff Drope, Zach Cahn, Cliff Douglas and Alex Liber

Photo Credit: Bud Ellison, « Smokers Cough » 2013 via Flickr