The Centers for Disease Control and Prevention (CDC) has issued a new review of tetanus in the United States, finding that 130 cases of the disease were reported between 1998 and 2000, a slightly higher figure than in the three years prior to the review period. More worrisome to agency officials, however, is that it estimates over half of Americans older than 20 years are not properly vaccinated against the disease. The group that appears most at risk for the illness are those above the age of 60 years, because they have neglected to remain current with their booster shots for tetanus, which should be administered every 10 years--or they were never vaccinated in the first place, as the vaccine only entered common use after World War II. Of note, the CDC found that just half of all tetanus infections in the three-year period under consideration were caused by puncture wounds--the cause most commonly associated with the disease.