The smoker's paradox during the COVID-19 pandemic? The influence of smoking and vaping on the incidence and course of SARS-CoV-2 virus infection as well as possibility of using nicotine in the treatment of COVID-19 - Review of the literature.

AIM OF THE STUDY: The study aims to present the current state of knowledge on the impact of traditional cigarettes and the nicotine contained in them on the incidence and course of SARS-CoV-2 infection. Moreover, we decided to exhibit the possibility of using this substance to treat COVID-19 infections. MATERIAL AND METHODS: The latest available scientific publications were reviewed until November 14, 2020, from the PubMed platform. RESULTS: Nicotine is a cholinergic agonist and pro-inflammatory cytokines inhibitor. Some authors present that smoking and nicotine reduce the amount of the ACE2 receptors which are used by the novel coronavirus to enter cells, while others claim that ACE2 receptors are upregulated in smokers. Moreover, the interaction of SARS-CoV-2 with nAChR is suspected of dysregulation of the nicotinic cholinergic system, which is associated with the pathophysiology of COVID-19. Due to the harmfulness of cigarettes, a high frequency of smokers is suspected among people suffering from COVID-19. However, some studies report that the number of current smokers hospitalized for SARS-CoV-2 infection is lower than expected, considering the prevalence of smoking in individual countries. Nicotine could restore the impaired function of the nicotine cholinergic system and possibly mitigate the cytokine storm. CONCLUSIONS: There is no clear attitude regarding the impact of smoking on the new coronavirus infection now. Researchers do not recommend smoking as a tool to combat the pandemic and show the importance of fighting addiction to reduce the adverse health effects of smoking. Both the relationship between cigarettes and the morbidity and severity of COVID-19, as well as the possibility of using nicotine in the treatment of the disease, require further analysis.

Impact of level of vitamin D in the body on the severity of COVID-19 - review of the literature.

INTRODUCTION: The aim of the study is to present the current state of knowledge on the influence of vitamin D levels on the severity of the course of COVID-19. MATERIAL AND METHODS: The latest available literature was reviewed until October 30, 2020 from the PubMed database. RESULTS: The literature reports that vitamin D has immunomodulatory and anti-inflammatory effects. It reduces the expression of cytokines such as IL-6, TNF-α and INF-γ, regulates the activity of T helper lymphocytes, and other elements of the immune system at the molecular level. The deficiency of this vitamin promotes the activation of the renin-angiotensin-aldosterone system, contributing to the development of acute respiratory distress syndrome. The severity of the course of SARS-CoV-2 infection depends on comorbidities, the development and course of which may also be affected by vitamin D levels (coagulopathies, pulmonary, cardiological, metabolic diseases). Most of the analyzed research studies from different countries indicated a relationship between insufficient vitamin D levels and a more severe course of COVID-19 and an increase in mortality due to it, especially among the elderly. Researchers agree that further analyzes are necessary concerning both the influence of the vitamin D blood serum levels on the morbidity and mortality due to COVID-19 as well as the use of its supplementation in the struggle against SARS-CoV-2 virus. There are reports of possible beneficial interactions of vitamin D with other substances, such as quercetin, estradiol, some microelements, and other vitamins. CONCLUSIONS: Maintaining an adequate level of vitamin D has a positive effect on the functioning of the immune system. At the moment, there is insufficient evidence to establish a clear relationship between vitamin D levels and the severity of COVID-19. It is necessary to conduct further research on a larger study group. The literature does not mention the use of vitamin D as a medication for COVID-19. People at risk of vitamin D deficiency should consider vitamin D supplementation at the current time of the pandemic.

The influence of vaccination against tuberculosis with the Bacillus-Calmette-Guérin(BCG) vaccine on COVID-19 incidence and mortality - review of the literature.

THE AIM OF THE STUDY: Is to present the state of knowledge from April and May 2020 about the influence of Bacillus-Calmette-Guérin vaccination against tuberculosis on incidence and mortality due to COVID-19. MATERIAL AND METHODS: A review of the latest literature till 9 May 2020 has been made. PubMed and ResearchGate databases and WHO reports were used. RESULTS: Immunomodulatory properties of the tuberculosis vaccine which protects against severe cases of tuberculosis and partly against other infections are indicated, including viral and respiratory infections. The BCG vaccine induces heterologous immunity and trained innate immunity. It was noted that in countries which maintain obligatory BCG vaccination COVID-19 incidence and mortality are lower than in countries that have stopped or never introduced BCG as mandatory vaccination. Most analysis confirmed this relationship, but they indicated the possible impact of other factors, such as genetics in the population, the type of strain from BCG vaccine, the level of health care and the wealth of a nation, the structure of migration, co-morbidities and a policy of introducing social distance. CONCLUSIONS: At the moment, we do not have enough evidence to support or deny the hypothesis of COVID-19 reduction in incidence and mortality in countries maintaining obligatory BCG vaccination. Other factors that might affect the results should be considered in further analysis. The results of clinical trials will provide more reliable proofs than analysis of epidemiological data. WHO does not recommend BCG vaccination to prevent COVID-19 and recommends it to newborns from areas with a higher incidence of tuberculosis.