Discussion

E-cigarettes were introduced to the U.S. market in 2007 (1). In 2018, 20.8% of high school students reported current e-cigarette use (5). E-cigarette use is markedly lower among U.S. adults than among youths; in 2018, only 3.2% of adults currently used e-cigarettes, with higher prevalences among persons aged 18–24 years (7.6%) and 25–34 years (5.4%) than among older age groups (6). Approximately three fourths of patients in this investigation were aged <35 years. In the general U.S. adult population, current e-cigarette use is slightly higher among males than females for both adults and youths (6); in the present investigation, approximately seven in 10 cases occurred in males. In this investigation, 62% of patients were aged 18–34 years; this is consistent with the age group with highest reported prevalence of marijuana use in the preceding 30 days in the United States (7).

THC-containing and nicotine-containing products were the most commonly reported substances used in e-cigarettes, or vaping products, by patients. Specific data on use of THC in e-cigarettes, or vaping products, in the general population is limited; among U.S. middle and high school students in 2016 who had ever used an e-cigarette, 30.6% reported using THC in an e-cigarette (33.3% among males and 27.2% among females) (8). Among adults who reported using marijuana in 2014, 9.9% reported consuming it via a vaporizer or other electronic device (11.5% among men and 7.8% among women) (9). In a recent study of college students, approximately 75% of those who had used substances other than nicotine in e-cigarettes reported using marijuana or THC-containing products in an e-cigarette (10). Because information about substance use in this investigation was self-reported, the information is not available for some cases because of the time required for completing and reporting patient interviews, inability to conduct interviews (e.g., patient refusal, loss to follow-up, persons who were too ill or died before they could be interviewed) and missing data for certain variables (e.g., patient refusal to answer certain questions). In addition, patients might not always know what substances they use or might be hesitant to reveal use of substances that are not legal in their state.

Continued monitoring of patient case counts and characteristics, as well as substances used with e-cigarette, or vaping, products, is critical to informing the ongoing investigation and helping to identify the cause. CDC and state health departments continue to collect and analyze epidemiologic data to better understand what types of devices and products patients are using (e.g., cartridges and e-liquids), the source of products or location where they were obtained, and the patterns (e.g., duration and frequency) of specific product use. Given the vast number of chemicals used in e-cigarette, or vaping, products, it is important to link epidemiologic data with findings from laboratory analyses of products and clinical specimens from patients. Federal, state, and private laboratories are working to collect and analyze products obtained from patients with lung injury associated with e-cigarette use, or vaping. In addition, CDC, clinical, and public health laboratories are collecting clinical specimens for future targeted analyses of substances identified in product samples.

The specific chemical exposure(s) causing this outbreak is unknown at this time. National data to date show that most lung injury patients with data on substance use report using THC-containing products with or without nicotine-containing products, although some patients report using only nicotine-containing products. While this investigation is ongoing, CDC recommends that persons consider refraining from using e-cigarette, or vaping, products, particularly those containing THC. Persons who continue to use e-cigarettes or vaping products should carefully monitor themselves and seek medical attention immediately if they have symptoms consistent with those described in this outbreak.§

Regardless of the investigation, e-cigarettes, or vaping products, should never be used by youths, young adults, pregnant women, or by adults who do not currently use tobacco products (2). Adults who use e-cigarettes because they have quit smoking should not return to smoking combustible cigarettes. In addition, persons who use e-cigarettes or vaping products should not get them from informal sources or off the street and should not modify e-cigarette, or vaping, devices or add any substances that are not intended by the manufacturer. Both THC-containing and nicotine-containing e-cigarette, or vaping, products purchased legally within states might also contain harmful substances (1); it is difficult for consumers to know what is in these products, and full ingredient lists are typically not available. THC use has been associated with a wide range of health effects, particularly with prolonged heavy use.¶ The best way to avoid potentially harmful effects is to not use THC, including through e-cigarette, or vaping, devices. Persons with marijuana use disorder should seek evidence-based treatment by a health care provider.

This investigation is ongoing. CDC will continue to work in collaboration with FDA and state and local partners to investigate cases and advise and alert the public on the investigation as additional information becomes available.