While 91 percent of children between the ages of 6 and 11 years are protected against both tetanus and diphtheria, protection declines to 47 percent among persons 20 years of age or older, and continues to decline over the years. In fact, only 30 percent of people 70 years of age and older are protected against both diseases. Therefore, it is critical to begin the tetanus-diphtheria booster vaccination process in adolescence, starting at age 11 or 12, followed by boosters every 10 years.

Some adults, mainly those over 60 years of age, may never have received a primary series of tetanus and diphtheria immunizations because these vaccines were not routinely given to children until 1950. For these people, a full adult series of three doses is necessary, followed by the booster every 10 years.

If you can't remember your last Td booster, aren't sure you ever had a Td vaccination, or are 60 or older, you may need a Td vaccination now. If you're not sure, call your doctor. Discuss your normal activities, travel plans and vaccination history to find out if you should get a Td booster today.

McQuillan GM, Kruszon-Moran D, Deforest A, Chu SY, Wharton M. Serologic immunity to diphtheria and tetanus in the United States. Ann Intern Med 2002;136: 660-666.