A POPULATION-BASED SEROLOGIC SURVEY OF IMMUNITY TO TETANUS IN THE UNITED-STATES

Background. Vaccination rates are frequently considered a surrogate me asure of protection. To provide more accurate estimates, serum levels of antibody against tetanus were measured as part of the third Nationa l Health and Nutrition Examination Survey (NHANES III), which studied a representative sample of the civilian, noninstitutionalized populati on of the United States. Methods. We measured tetanus antitoxin using a solid-phase enzyme immunoassay in serum samples from 10,618 persons six years of age and older who were examined during phase 1 of NHANES III in 1988 to 1991. Results. Overall, 69.7 percent of Americans six y ears of age and older had protective levels of tetanus antibodies (>0. 15 IU per milliliter). The rate decreased from 87.7 percent among thos e 6 to 11 years of age to 27.8 percent among those 70 years of age or older, Among children 6 to 16 years of age, 82.2 percent had protectiv e levels of tetanus antibodies, with little variation according to rac e or ethnicity. More men than women were immune (79.0 percent vs. 62.4 percent). Mexican Americans had a significantly lower rate of immunit y (57.9 percent, P<0.05) than either non-Hispanic whites (72.7 percent ) or non-Hispanic blacks (68.1 percent). Those with a history of milit ary service, higher levels of education, or incomes above the poverty level were more likely to have protective antibody levels. Although th e prevalence of immunity declined rapidly starting at the age of 40 ye ars, most of the 107 cases of tetanus (with 20 deaths) reported in 198 9 and 1990 occurred in persons 60 years of age or older, Conclusions. Despite the fact that effective vaccines against tetanus have been ava ilable since the 1940s, many Americans do not have immunity to tetanus , and the rates are lowest among the elderly There is an excellent cor relation between vaccination rates (96 percent) and immunity (96 perce nt) among six-year-olds. However, antibody levels decline over time, a nd one fifth of older children (10 to 16 years of age) do not have pro tective antibody levels.