Smokers are up to 80 percent more likely to require hospitalization and die from COVID-19, according to a new study that tracked more than 400,000 people with the the virus.

The study, published in the British journal Thorax, also found genetic predisposition to smoking was associated with a 45 percent higher risk of infection and a 60 percent  to 80 percent higher risk of hospitalization because of COVID-19.

The researchers used health records, COVID-19 tests results, hospital admissions data and death certificates of 421,469 participants in the UK Biobank study between January and August to assess the link between smoking and illness severity.

The Centers for Disease Control and Prevention has listed smoking among medical conditions that increase the risk of severe illness from COVID-19. More than a year ago, U.S. health experts also warned that vaping among teens and young adults could increase COVD-19 risks.

“We believe that younger people who vape, or use e-cigarettes, run an even higher risk of contracting COVID-19, and more severely, than other people,” said Dr. J. Craig Allen, medical director of Rushford, part of the Hartford HealthCare Behavioral Health Network, during the pandemic’s early stages. “Vaping leaves the lungs more vulnerable to severe infection and we know that COVID-19 attacks the lungs.”

Previous studies, mostly observational, could not quantify the risk of smoking and COVID-19. One study lasts year actually suggested smoking could protect against the virus. That study was later retracted after some of the paper’s author reportedly had financial links to the cigarette industry.

Here is the CDC’s list of medical conditions increase the risk of severe illness from COVD-19:

  • Cancer.
  • Chronic kidney disease.
  • Chronic lung diseases.
  • Dementia or other neurological condition.
  • Diabetes (Type 1 or Type 2).
  • Down syndrome.
  • Heart conditions.
  • HIV infection.
  • Weakened immune system.
  • Liver disease.
  • Obesity or overweight.
  • Pregnancy.
  • Sickle cell disease or thalassemia, a blood disorder.
  • Smoking (current or former).
  • Solid organ or blood stem cell transplant.
  • Stroke or cerebrovascular disease (affecting blood flow to the brain).
  • Substance use disorders.

Already, smoking is associated an elevated risk of heart disease, cancer, lung disease stroke and diabetes and other medical conditions.

“If you currently smoke, quit,” says the CDC. “If you used to smoke, don’t start again. If you’ve never smoked, don’t start.”