World War II poster urging the British public to immunise against diphtheria. The disease is caused by the bacterium Corynebacterium diphtheriae and most commonly affects the throat, causing swelling of the mucous membranes. The danger to the patient is two-fold: the swelling may form an obstruction to breathing, and the bacteria secrete a toxin which passes into the blood. The toxin may cause failure of the kidneys, heart muscles or local paralysis. This poster was published by the Ministry of Health and the Central Council for Health Education.