Why smokers get sicker: tobacco and the immune system

Immunity starts with physical barriers. The cilia that sweep pathogens out of the airways are paralyzed and destroyed by smoke, so bacteria that would normally be evicted within minutes stay long enough to establish infection.

The mucous membranes of the nose and throat dry out and crack, and the tight junctions between airway cells loosen, opening doors that should stay shut.

Smoking alters nearly every immune cell type studied: macrophages in the lung become less efficient at swallowing bacteria, neutrophils behave more destructively toward tissue, natural killer cell activity drops and antibody responses weaken.

The overall picture is paradoxical and dangerous: worse defense against invaders, plus more chronic inflammation damaging your own tissue. This mix is why smokers both catch more infections and suffer more autoimmune and inflammatory disease.

Pneumococcal pneumonia: smoking is one of the strongest independent risk factors in otherwise healthy adults.

Influenza: smokers are more likely to be infected and more likely to have severe disease.

Tuberculosis: smoking increases both the risk of infection progressing to active disease and the risk of dying from it. The WHO treats tobacco as a major driver of the global TB burden.

Invasive meningococcal disease: smoking and secondhand smoke exposure raise risk, particularly in adolescents.

Surgical site infections: smokers have significantly higher rates, which is why pre-operative cessation programs exist.

Studies have found weaker antibody responses to several vaccines in smokers, meaning even prevention works less well.

The good news is speed: immune parameters begin improving within weeks of quitting, and the airway barrier restores itself over the following months. Ex-smokers report fewer and shorter respiratory infections, usually within the first year.