Tetanus immunization status and immunologic response to a booster in an emergency department geriatric population

Abstract

Although effective procedures for the prevention of tetanus have long been available, serosurveys done since 1977 demonstrate that 49% to 66% of the elderly population lacks a protective antitoxin level (more than 0.01 IU/mL). This study was undertaken to assess the tetanus immunization status of patients presenting to an emergency department and to evaluate their immunologic response to a tetanus booster. The study was conducted in a tertiary care ED. The patients enrolled were 65 or more years old and had breaks in their skin barriers. At each patient's initial presentation, pertinent demographic data and tetanus immunization history were recorded. The patient was then followed for 21 days. Each patient's antitoxin titer was determined on a serum sample by ELISA, and, if required by the Advisory Committee on Immunization Practices criteria, a booster was administered at the first visit. Serum antitoxin assays were repeated on days 7, 14, and 21 after the initial visit until seroconversion (titer more than 0.01 IU/mL). Forty-four patients (55%) had protective levels at initial presentation, and in 36 (45%) the levels were not protective. Age and sex were not predictive of protection. Past military service and a definite history of three or more previous immunizations were good predictors of protection. Of 34 patients who were followed serially for inadequate initial titers, only 19 (56%) seroconverted by day 14. Patients who did not seroconvert were more likely to be older (P less than .05). This study demonstrated that a significant number of elderly patients lacked an initial protective level of tetanus antitoxin. Of these, 44% failed to seroconvert within 14 days and carried a potential risk of developing tetanus.