Because tetanus infections often are fatal, vaccination is important. A primary series of three injections given over a six-month period should be administered in childhood or to an adult who has not already received the primary series in childhood. A booster dose of the vaccine should be given to adults every 10 years. Diphtheria is a very contagious and potentially life-threatening infection. It can attack the nerves and heart and leave victims with severe, life-long complications. The tetanus vaccine is available alone or in combination with a diphtheria vaccine administered in a single injection.