Science

Does smoking protect against COVID-19? Links between smoking and coronavirus infection still unclear

Researchers have suggested that smoking may protect against severe forms of COVID-19. Is it really the case?

Protecting yourself from COVID-19

June 15, 2021

In 2020, researchers suggested that smoking could protect against severe forms of COVID-19 and many media outlets picked up on the information. Since then, the main paper that assumed a protective effect of smoking against COVID-19 has been depublished due to undeclared links of interest between some of the authors and the tobacco industry. So, does smoking really protect against COVID-19? What would be the links between smoking and coronavirus infection?

The still unclear links between smoking, coronavirus infection and ACE-2 receptors

Coronaviruses, such as SARS-CoV2 which plunged the world into an unprecedented global crisis, enter the body mainly by binding to a cell surface protein: ACE-2 receptors. These components are involved in pulmonary and cardiovascular function, through the production of a substance that dilates blood vessels: angiotensin 1-7. This dilation mechanism acts in principle in balance with a vessel contraction mechanism, operated by angiotensin II. However, in some cases, such as in high blood pressure (a condition frequently linked to smoking), this balance is disrupted and leads to health problems.

But why would smoking protect against COVID-19? Researchers have speculated that the number of these ACE-2 receptors may be altered by the intake of nicotine (the addictive substance in tobacco), either up or down. However, the studies are contradictory, and it's not possible to draw a definitive conclusion on this potential link between smoking, coronavirus infection and ACE-2 receptors. Nevertheless, this mechanism is one of the avenues being explored in the search for a treatment for COVID-19. Some Parisian hospitals are currently studying the impact of nicotine on coronavirus infection risks among caregivers.

Smoking is also associated with many cardiovascular and respiratory diseases, and is known to increase the severity of infections. Several studies have already shown that smokers suffering from influenza, pneumonia, or bronchiolitis, generally had a more unfavorable evolution of their condition than non-smokers. Rather than protecting, smoking would rather increase the risk of being affected by a serious form of coronavirus.

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What can you do to protect yourself from COVID-19?

In any case, health institutions strongly recommend to stop smoking, and not to take nicotine replacement therapy in order to protect yourself against COVID-19, because nothing to date allows to establish a causal link between nicotine intake, ACE-2 receptor expression, vulnerability to the virus, and, if applicable, the severity of the infection. Indeed, even if it were finally demonstrated that nicotine has a protective effect against coronaviruses, smoked tobacco contains thousands of other toxic substances of which several dozen are carcinogenic. Moreover, the dose and the mode of administration of pure nicotine would still have to be established, undoubtedly on a case by case basis.

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