08/06/2020

How does tobacco intake influence SARS-CoV-2 infection?

Summary:

  1. There are reports based on a small group of patients showing that smokers were in the minority among patients infected with SARS-CoV-2.
  2. Analyses of small groups of patients showed more severity and higher mortality among active smokers.
  3. There isn’t enough data to draw a conclusion on the positive or negative influence of tobacco on COVID-19 infection.
  4. Tobacco is harmful to the health of smokers and people in their close proximity even without COVID-19.

COVID-19 pandemic is still proceeding with over 6’500’000 people already infected [1]. Scientists and governments around the world are still looking for ways to prevent the spread of the SARS-CoV-2 and to effectively cure people who are already infected with the virus.

Every new discovery generates a lot of media coverage even without result verification, often causing confusion among the readers and viewers of the news. Recent news showed two vastly different results regarding the influence of smoking tobacco on the infection rates and progression of the COVID-19 disease. On the one side, there were reports about smokers being less susceptible to the infection with the SARS-CoV-2 [2, 3]. On the other side, there were news articles claiming that smokers are more prone to develop severe symptoms of COVID-19 disease [4, 5].

Smoking requires keeping hands close to the face, which increases the risk of spreading the SARS-CoV-2 virus to your mouth or nose. As smoking often happens in groups there is a higher possibility to infect each other. This figure was inspired by an infographic published by WHO Europe, “Coronavirus (COVID-19) and tobacco use”. Figure prepared by Ambra Villani.
Smoking requires keeping hands close to the face, which increases the risk of spreading the SARS-CoV-2 virus to your mouth or nose. As smoking often happens in groups there is a higher possibility to infect each other. This figure was inspired by an infographic published by WHO Europe, “Coronavirus (COVID-19) and tobacco use”. Figure prepared by Ambra Villani.

The primary source for the former side is a preprint article based on the results collected from a group of 482 patients hospitalized in a single French university hospital [6]. From a survey run among patients infected with SARS-CoV-2, they discovered that only 5.3% of them were smoking daily. At the time it was shown that 25.4% of the French population was smoking daily. Similar results were then presented for 441 patients admitted to one of the hospitals in Italy [7]. With 14.9% of Italian population smoking in the tested age group, it was shown that only 5% of COVID-19 patients were active smokers, and 10% used to smoke in the past. Furthermore, reports based on 393 patients from two hospitals in New York and 1099 patients from 552 hospitals in China showed similar results [8, 9].

While it is too early to say how tobacco use influences the development of COVID-19, it is known that smoking causes damage to organs like lungs or larynx, and negatively influences the immune system. These could lead to less effective defenses against the SARS-CoV-2 by our bodies. This figure was inspired by an infographic published by WHO Europe, “Coronavirus (COVID-19) and tobacco use”. Figure prepared by Ambra Villani.
While it is too early to say how tobacco use influences the development of COVID-19, it is known that smoking causes damage to organs like lungs or larynx, and negatively influences the immune system. These could lead to less effective defenses against the SARS-CoV-2 by our bodies. This figure was inspired by an infographic published by WHO Europe, “Coronavirus (COVID-19) and tobacco use”. Figure prepared by Ambra Villani.

On the contrary, results from the same reports from both Italy and China showed that, among smoking patients, a higher percentage developed severe symptoms or died from the disease when compared to non-smokers [7, 9]. The rest of the publications mentioned before didn’t include information on the severity of the disease. Moreover, another study from China statistically analyzed 13 different reports regarding the severity and mortality of COVID-19 [10]. Of these 13 reports, only 5 included information regarding smoking, with the total number of studied smoker cases of 1983. After statistical analysis, they concluded that smoking males above 65 are most susceptible to developing severe symptoms or even dying after infection with SARS-CoV-2. Furthermore, a group from the USA analyzed tissues from the lungs and mouths of smokers and non-smokers [11]. They presented higher ACE2 gene levels in smokers. ACE2 is a receptor in humans responsible for binding with the SARS-CoV-2 virus. This could lead to easier infection with the virus.

Second-hand smoking can increase the risk of respiratory infections in people around you. This figure was inspired by an infographic published by WHO Europe, “Coronavirus (COVID-19) and tobacco use”. Figure prepared by Ambra Villani.
Second-hand smoking can increase the risk of respiratory infections in people around you. This figure was inspired by an infographic published by WHO Europe, “Coronavirus (COVID-19) and tobacco use”. Figure prepared by Ambra Villani.

Recently, WHO released a scientific brief in which they recommend not consuming tobacco products [12]. While all of the presented results are certainly interesting and worth further investigation, they mostly come from far too small test groups to draw any meaningful conclusion. There are certainly well known harmful effects of smoking, but at this point, it is hard to say with full certainty that tobacco influences the outcome of infection with the SARS-CoV-2, and further investigation is required. Unfortunately, reactive and unreviewed coverage of these topics can certainly cause a lot of distrust toward scientists and scientific research.

References:

  1. WHO, Coronavirus disease (COVID-19) Situation Report – 139. 2020, World Health Organization.
  2. Samuel, H., Smokers ‘four times less likely’ to contract Covid-19, prompting nicotine patch trials on patients, in The Telegraph. 2020.
  3. Crist, C., Smokers Hospitalized Less Often for COVID-19, in WebMD. 2020.
  4. Wilson, C., Smoking probably puts you at greater risk of coronavirus, not less, in NewScientist. 2020.
  5. Dembosky, A., Fear Of Contracting Coronavirus Propels Some Smokers To Quit, in npr. 2020.
  6. Miyara, M., et al., Low incidence of daily active tobacco smoking in patients with symptomatic COVID-19. Qeios, 2020.
  7. Gaibazzi, N., et al., Smoking Prevalence is Low in Symptomatic Patients Admitted for COVID-19. medRxiv, 2020.
  8. Goyal, P., et al., Clinical Characteristics of Covid-19 in New York City. N Engl J Med, 2020.
  9. Guan, W.J., et al., Clinical Characteristics of Coronavirus Disease 2019 in China. N Engl J Med, 2020. 382(18): p. 1708-1720.
  10. Zheng, Z., et al., Risk factors of critical & mortal COVID-19 cases: A systematic literature review and meta-analysis. J Infect, 2020.
  11. Chakladar, J., et al., Smoking-Mediated Upregulation of the Androgen Pathway Leads to Increased SARS-CoV-2 Susceptibility. Int J Mol Sci, 2020. 21(10).
  12. WHO, Smoking and COVID-19: Scientific brief. 2020, World Health Organization.
Kamil Wolanin
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