Concurrent use of e-cigarettes and cannabis and associated COVID-19 symptoms, testing, and diagnosis among student e-cigarette users at four U.S. Universities

•COVID-19 symptoms were prevalent among concurrent e-cigarette and cannabis users.•COVID-19 diagnoses were prevalent among concurrent e-cigarette and cannabis users.•Frequent concurrent users were more likely to report COVID-19 symptoms.•Frequent concurrent users were more likely to report COVID-19 diagnoses.•Students should be educated on risks of e-cigarette and cannabis use and COVID-19.