IMMUNOLOGICAL RESPONSE TO TETANUS TOXOID IN THE ELDERLY - ONE-YEAR FOLLOW-UP

Study objective: To determine whether elderly patients documented to h ave nonprotective titers of anti-tetanus antibodies (ATA) are able to achieve and maintain protective ATA titers for at least 1 year after t etanus immunization. Methods: Thirty-five outpatients aged 65 or older with documented inadequate ATA titers were given 1 tetanus immunizati on. Repeat titers were obtained 2 months and 12 months after immunizat ion. Titers were measured with an enzyme-linked immunoassay kit (Binda zyme kit). ATA titers in excess of .17 IU were considered protective. The study was conducted at a large urban geriatric center. Results: Th e mean age of participants was 78.7 years; 86% (24/28) were women. Rep eat ATA titers were obtained an average of 122 days and 493 days after immunization. The mean preimmunization ATA titer was .1 IU, (range .0 4 to .16 IU). After immunization, the 2-month ATA titer rose a mean of .61 (95% confidence interval [CI].35 to .87) IU, with 86% (30/35) ach ieving protective titers. After 1 year only 28 of 35 patients were ava ilable for follow-up. Protective titers had been present in all 7 pati ents lost to follow-up. After 1 year, 82% (23/28) patients had protect ive titers. The mean ATA titer for the 28 patients was .54 (95% CI -.7 8 to 1.86) ill, a significant increase from preimmunization levels (P = .002). However, ATA titers changed -.18 (95% CI -.98 to .62) IU betw een 2 months and 1 year(P = .02). There was no correlation between gen der, country of birth, and medical history with development or mainten ance of protective titers. Conclusion: Administration of 1 tetanus tor oid affords protective immunization to a large portion of the elderly population after 1 year.