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MARIPOSA – When someone’s lungs are exposed to flu or other infections the adverse effects of smoking or vaping are much more serious than among people who do not smoke or vape.
Smoking makes COVID worse if you get it and smoking — and vaping — increase the risk of being infected and developing COVID-19.
As of April 28, 2020 there were 19 peer reviewed papers that had data on smoking and COVID disease progression, 17 from China, 1 from Korea, and 1 from the US. Our peer reviewed meta-analysis of these 19 papers found that smoking was associated with more than a doubling of odds of disease progression in people who had already developed COVID.
There have been several reports, mostly in non-peer reviewed preprints, reporting lower levels of COVID-19 infections among smokers than nonsmokers. This is a surprising finding because, based on what we know about the effects of smoking and vaping on immune function of the respiratory system, one would expect that smoking and vaping would increase risks of COVID infection. A big problem with all the studies to date has been that they have been based on people who were tested, rather than samples drawn from the population as a whole. Because of limited availability of tests in many places, the resulting samples are biased toward people who may already have symptoms.
On August 11, 2020, Shivani Mathur Gaiha and Bonnie Halpern-Felsher from Stanford and Jing Cheng from UCSF addressed this problem in a study that used a population-based sample of youth and young adults, “Association between youth smoking, electronic cigarette use and Coronavirus Disease 2019. Among young people (ages 13-24) COVID-19 diagnosis was five times more likely among ever-users of e-cigarettes only, seven times more likely among ever-dual-users, and 6.8 times more likely among past 30-day dual-users.
These findings are particularly important as the case mix of people getting COVID is moving to younger people, perhaps reflecting increased exposures due to reduced social distancing and a lack of understanding about factors exacerbating COVID-related risk in this age group.
Smoking is associated with increased development of acute respiratory distress syndrome (ARDS) in people with a risk factor like severe infection, non-pulmonary sepsis (blood infection), or blunt trauma. People who have any cotinine (a metabolite of nicotine) in their bodies – even at the low levels associated with second-hand smoke – have substantially increased risk of acute respiratory failure from ARDS (paper 1, paper 2, paper 3).
The recent excellent summary of the evidence on the pulmonary effects of e-cigarettes reported multiple ways that e-cigarettes impair lungs’ ability to fight off infections:
Effects on immunity
Reporting of respiratory symptoms by e-cigarette users suggests increased susceptibility to and/or delayed recovery from respiratory infections. A study of 30 healthy non-smokers exposed to e-cigarette aerosol found decreased cough sensitivity.82 If human ciliary dysfunction is also negatively affected, as suggested by animal and cellular studies,83 the combination of reduced coughing and impaired mucociliary clearance may predispose users to increased rates of pneumonia. Exposure to e-cigarettes may also broadly suppress important capacities of the innate immune system. Nasal scrape biopsies from non-smokers, smokers, and vapers showed extensive immunosuppression at the gene level with e-cigarette use.84 Healthy non-smokers were exposed to e-cigarette aerosol, and bronchoalveolar lavage was obtained to study alveolar macrophages.46 The expression of more than 60 genes was altered in e-cigarette users’ alveolar macrophages two hours after just 20 puffs, including genes involved in inflammation. Neutrophil extracellular trap (NET) formation, or NETosis, is a mode of innate defense whereby neutrophils lyse DNA and release it into the extracellular environment to help to immobilize bacteria, a process that can also injure the lung.85 Neutrophils from chronic vapers have been found to have a greater propensity for NET formation than those from cigarette smokers or non-smokers.57 Given that e-cigarettes may also impair neutrophil phagocytosis,86 these data suggest that neutrophil function may be impaired in e-cigarette users. [emphasis added]
Studies in animals reinforce and help explain these human effects:
Two weeks of exposure to e-cigarette aerosol in mice decreased survival and increased pathogen load following inoculation with either Streptococcus pneumoniae or influenza A, two leading causes of pneumonia in humans.97 Furthermore, the aerosol exposure may lead to enhanced upper airway colonization with pathogens and to virulent changes in pathogen phenotype, as shown with Staphylococcus aureus.98 99 Thus, although more studies are needed, the animal data suggesting that vaping leads to an increased susceptibility to infection would seem to correlate with the population level data in young adult humans, whereby vapers have increased rates of symptoms of chronic bronchitis.23 [emphasis added]
A meta-analysis of the relationship between smoking and influenza found that smokers were more likely to be hospitalized and admitted to the ICU.
Dr. Nora Volkow, director of the National Institute on Drug Abuse, posted an article on her blog “COVID-19: Potential Implications for Individuals with Substance Use Disorders,” that stared off by saying
As people across the U.S. and the rest of the world contend with coronavirus disease 2019 (COVID-19), the research community should be alert to the possibility that it could hit some populations with substance use disorders (SUDs) particularly hard. Because it attacks the lungs, the coronavirus that causes COVID-19 could be an especially serious threat to those who smoke tobacco or marijuana or who vape.
She goes on to address other drug use and how COVID-19 could interact with them, including noting that vaping, like smoking, may also harm lung health. Whether it can lead to COPD is still unknown, but emerging evidence suggests that exposure to aerosols from e-cigarettes harms the cells of the lung and diminishes the ability to respond to infection. In one NIH-supported study, for instance, influenza virus-infected mice exposed to these aerosols had enhanced tissue damage and inflammation.
The California Department of Public Health has information on smoking, vaping and COVID here, as does the California Smokers’ Helpline. Trinity Health is also urging people to stop smoking to protect against COVID-19. FDA has said that vaping and smoking could increased COVID risks. CDC lists smoking as one of the risk factors for COVID-19 because smoking depresses immune function.
UCSF has added smoking and vaping nicotine and cannabis to COVID-19 triage protocol. Doing so will both improve patient care and, over the longer term, provide important information needed to quantify how smoking and vaping impact COVID risks.