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Since the beginning of the Coronavirus epidemic most of the experts have been faced with a huge amount of often unexplained questions, leading to conflicting discussions in the media.
One of the recent publications looked into the eventual protective action of smoking against Coronavirus infection.
The aim of this contribution is to present various points of view and comment on them.
It all began with a French study at the Pitiè-Salpetrère in Paris, which indicated that in both hospitalized and non-hospitalized patients, compared to the general population, daily smokers showed a much lower probability of contracting SARS-CoV-2 either symptomatic or with a severe course. Out of 500 patients, 350 hospitalized and 150 outpatients, only 5% were smokers (Zahir Amoura). This would mean an 80% lower risk for smokers compared to non-smokers.
This publication prompted a very heterogeneous explanation from internationally famous scientists:
1) Robert Koch Institute (e-mail reply to Mr. Kutzner, Screenshot: Corrective): “Dear Mr. Kuntzer, thank you for your mail. The few studies, including two revisions (Scinexx 2020), rather consider smoking as a risk factor for smokers for a severe course of Covid-19 (see comment A), but theevidenceis insufficient due to the low number studied, even if it seems pathophysiologically correct (see comment B).There is however a discussion on the internet, for example in China, where there is a very high prevalence of smokers, who were far less represented in some studies, whereby in the light of current evidence, smoking could have a protective effect. The Robert Koch Institute is unable to specifically accept this latest line of argument.”
Comment A: at the end of March the scientific journal Scinexx found a marked risk in smokers, because nicotine facilitatesthe connection between coronavirus and cell receptors.
Comment B: Statistical analyses of a study on 11 patients, as in this case, have no value.
“Nicotine adheres to the cell receptors, which are also used by the Coronavirus “ (Prof. Jean-Pierre Changeux from the Pasteur Institute and the Collège de France).
- Nicotine or other substances in tobacco smoke “could play a protective role” (Prof. Dr. Bernd Mayer, Graz University).
- “Smokers have a reduced level of Ace2 receptors” (European Journal of Internal Medicine).
- “This study is not sound, there is certainly no protective effect from tobacco smoke” (Dr. Georg-Christian Zinn, Head of the Hygienezentrum Bioscientia).
- “Smokers have a base higher risk of contracting viral infections. Therefore smokers get infected faster by Coronavirus” (Prof. Michael Pfeiffer, President of the German Pneumology Society).
To put everything on a single denominator as regards Coronavirus, we need only to accept the theory, long since proposed to the scientific community (never contradicted until now), that Coronavirus is only transmitted by aerosol.
This theory postulates that Coronavirus is not transmitted by droplets or contact, but exclusively by aerosols (exhaled air), in badly ventilated, crowded environments, in the presence of people with Coronavirus (Sick Building Syndrome).
Smokers spend more time outdoors than non-smokers (also because of the smoking ban in closed spaces). Furthermore during lockdown the time spent in closed spaces (homes) increased more than smoking due to the psychological situation. This led to an increase in the ventilation of the homes (also by non-smoking housemates), and so the viral load to induce a significant infection is not achieved.
