Since the pandemic started to hit the US in full force in March, speculation about the link between vaping and Covid-19 has flourished. The Food and Drug Administration and the National Institute on Drug Abuse both issued warnings. Anecdotal reports of young vapers coming down with severe coronavirus infections began to crop up. But there was very little research to support a connection.
Now, a study published today in The Journal of Adolescent Health finally offers data that shows a relationship between e-cigarette use and Covid-19 risk. Researchers from Stanford University show that teenagers and young adults ages 13 to 24 who use e-cigarettes are five times more likely to be diagnosed with Covid-19 than their non-vaping peers. Those who are dual users—people who smoke both traditional and electronic cigarettes—are seven times more likely to test positive for the virus, the researchers found.
“I knew there would be a relationship,” says coauthor Bonnie Halpern-Felsher, a professor of pediatrics at Stanford University who studies youth tobacco use. “I did not expect it to be this strong of a relationship.”
Studies have already linked smoking with higher susceptibility to severe Covid-19 infections, but previously no population-based studies had examined the link between e-cigarette use and Covid-19 in teenagers and young adults. The question researchers wanted to answer was two-fold: Were e-cigarette smokers more likely to get tested for SARS-CoV-2? And were they more likely to test positive? “The answer is soundly yes” to both parts of the question, says Halpern-Felsher.
The researchers gathered their data through an online survey posted on spaces like social media and gaming sites. Over 4,000 teens and young adults from all 50 states responded, completing the roughly 15-minute survey. Researchers then weighted the samples to reflect the racial and ethnic, gender, LGBTQ status, and age makeup of the United States population.
The survey, which was sent out in early May, asked respondents whether they had ever used regular or electronic cigarettes; whether they had used them in the last 30 days; whether they had been tested for Covid-19; and whether their test results came back positive. The researchers also controlled for other Covid-19 risk factors like whether the respondents lived near a coronavirus hotspot; whether they were under- or overweight, which can affect lung function; and for their socio-economic status, which can affect how well people can socially distance. Ultimately, the researchers determined that dual users who had smoked in the last 30 days were not only more likely to test positive, but they were also nine times more likely to get tested in the first place.
The survey did not explore why users decided to get tested. It’s possible that users confused the effects of vaping—extra phlegm, coughing, or shortness of breath—with Covid-19 symptoms. But the high rate of positive test results may indicate that vapers are more vulnerable to the virus itself.
That said, this study simply illustrates a correlation between e-cigarette and cigarette use and positive Covid-19 diagnoses. As the authors explain in the paper, their findings “show that e-cigarette use and dual use of e-cigarettes and cigarettes are significant underlying risk factors for COVID-19 that has previously not been shown.” But on its own, this paper can’t prove whether they may be more biologically susceptible to infection in the first place, or if they are more likely to have severe infections.
Still, Halpern-Felsher has a few theories for why this overlap might exist. Smokers may have more lung damage, making them more susceptible to the virus. Or they might be touching their hand to their mouth more often than other people, or sharing vapes, increasing their likelihood of being exposed in the first place. Or it could be that the virus is being spread through the aerosols vapers exhale. “Those are all hypotheses,” she says. “Someone needs to follow it up.”
There are already studies that link smoking tobacco with a higher risk of Covid-19. A study published in March in the European Respiratory Journal found that smokers and those with chronic obstructive pulmonary disease had greater expression of ACE2, the protein SARS-CoV-2 uses to enter cells. In a meta-analysis of 19-papers published in May in the journal Nicotine and Tobacco Research, scientists from UC San Francisco found that tobacco use nearly doubled a person’s risk of severe Covid-19 infection. Another study by a separate group of researchers at UCSF published in the Journal of Adolescent Health in July found that smoking also doubled the risk of Covid-19 infection for young adult ages 18 to 25.
“I’m not at all surprised” by the results of the Stanford survey, says Sharon Levy, director of the Adolescent Substance Use and Addiction Program at Boston Children’s Hospital, who was not involved in the study. She points out that nicotine can inhibit the immune system and e-cigarettes can affect a lipid layer in the lungs that traps viruses, bacteria, and other foreign particles, as well as the macrophages that clear those threats away. It can also decrease the number of hair-like projections called cilia that help clear pathogens out of the lungs. “We’re appreciating more and more that vaping is associated with lung injury,” says Levy. When the lungs are injured, she says, they’re less likely to be able to fend off infections.
More and more evidence shows that e-cigarettes make the lungs more vulnerable to a variety of different infections, which could potentially provide a mechanistic explanation for the relationship the Stanford study shows. “There’s been a consensus that vaping and the use of e-cigarettes causes a suppression of respiratory immune responses,” says Ilona Jaspers, a pediatrician, toxicologist, and deputy director of the University of North Carolina’s Center for Environmental Medicine, Asthma, and Lung Biology, who was not involved in the study. She says that models in both mice and in human lung tissue show that e-cigarettes reduce the host’s ability to respond to viral and microbial threats.
Alicia Casey, a pulmonologist also at Boston Children’s Hospital who works with kids and teens and was not part of this study, says she’s seen similar problems in healthy teens who couldn’t fight off other viral infections. “We definitely saw this with the flu this year,” she says. “Why are these teenagers having so much trouble with the flu? An otherwise-healthy high school athlete should not have trouble and shouldn’t have chronic respiratory problems either.” Casey says that vaping is associated with damage to the lower respiratory tract, so it makes sense that vapers with underlying damage to their respiratory system would have trouble fighting off an infection to that system.
Casey adds that the Stanford paper is particularly concerning given that data from a 2019 national survey indicates that more than a quarter of high school students use e-cigarettes. “We may have a lot of young people struggling with this,” she says, especially as states begin to reopen and kids go back to school or start to see their friends more often.
Levy points out that some risk factors may also be behavioral. “The way I see it, nicotine vaping is a marker for other kinds of behaviors that all may increase risk,” she says. Like Halpern-Felsher, she notes that teens and young adults who vape may share vape pens, that smoking involves a lot of hand-to-mouth contact, and that it creates aerosols, all of which could increase the risk of passing the virus. Plus, people may also be vaping marijuana or drinking—if they’re feeling less inhibited, they may forget to follow protocols like wearing a mask or social distancing. “That’s why it’s so frightening,” Levy says. “They’re more likely to behaviorally get themselves into trouble, and then they’re also more likely to experience worse outcomes.”
But while the exact mechanism of how vaping and Covid-19 are correlated is still unknown, there’s already political pressure on legislators to act. Representative Raja Krishnamoorthi, chairman of the House Subcommittee on Economic and Consumer Policy, cited the study in a letter to the FDA published today, asking the agency to take e-cigarettes off the market during the pandemic, writing that it is “evident that the youth vaping epidemic has combined forces with the Coronavirus pandemic, creating a much deadlier foe that demands FDA action.”
Halpern-Felsher says both physicians and young e-cigarette users should pay attention to the survey findings. “We’re hoping there’s a prevention message out there: Adolescents, young adults, take note that this is going to put you at risk,” she says. She also urges healthcare providers to regularly ask young people about their vaping and smoking habits. That will help determine who is at risk. Meanwhile, being able to track the number of people who both use e-cigs and come in for Covid-19 testing and treatment will also help researchers figure out whether vaping contributes to more severe coronavirus infections. “We definitely need more data,” she says.