Considerations on the article De Bernardis, E., & Busà, L. (2020). A putative role for the tobacco mosaic virus in smokers’ resistance to COVID-19 Medical Hypotheses, 110153

A putative role for the tobacco mosaic virus in smokers’ resistance to COVID- 19 was supposed by de Bernardis and co-authors. However, there are several issues that need to be addressed: putative “high mortality rate of smokers infected by SARS-CoV-2”, “poor collection of medical history details in an emergency situation”, reverse causation (i.e. smokers with severe symptoms may stop smoking before admission to hospital and therefore be counted as non-smokers; alternatively, people presenting with COVID-19 may be less likely to admit to being current smokers); self-selection (smokers with COVID-19 may be less likely to present to hospital, either because they have died or they self-treat in the community, e.g. because of lack of access to funds, given that smoking has a strong negative association with socio-economic position); cohort effects (smoking prevalence declines with age and older people are more likely to be hospitalised if they are infected). Other authors showed that smoking increases the risk of severe COVID-19 by around two-fold and meta-analyses reported higher prevalence of comorbidities, many of which are tobacco-related diseases, in patients with severe COVID-19 reporting an OR = 2.25 (95% CI: 1.49–3.39) for developing severe Covid-19 among patients with a smoking history. In the light of all these considerations, the validity of the affirmation made by de Bernardis and colleague about the “resistance of tobacco smokers to the SARSCoV-2 infection”, either for infection, or for progression and severity of COVID-19, is not convincing.