It’s been understood for decades that tobacco smoking is the single leading cause of lung cancer, causing an estimated 1.5 to 2 million deaths per year. Eighty-five percent of lung cancers occur in current or former smokers. This year, there is a new reason to quit smoking: COVID-19. Recent studies indicate that when infected with the novel coronavirus, tobacco smokers are more likely to develop severe infections, to need mechanical ventilation, and to die as a result of the illness. This is not surprising, given that smoking causes damage that inhibits the lungs’ ability to clean and repair themselves. Along with getting plenty of exercise, eating healthy, and managing stress, avoiding cigarettes is one if the top ways to keep your immune system in good working order during the pandemic.