Decline of Tetanus Antitoxin Level with Age in Taiwan

Abstract

Tetanus is caused by Clostridium tetani, and is a vaccine-preventable infectious disease. The purpose of this study was to investigate the degree of protective tetanus immunity among adolescents and adults in Taiwan, which may provide valuable information for recommendations for tetanus vaccination strategy. Individuals aged 16 years or older who were visiting a local hospital for health examinations were invited to participate in the study. Participants' serum levels of tetanus antitoxin were measured. A standard questionnaire was used to collect demographic data and information about risk factors. The prevalence of protective tetanus immunity in various age groups was described and sociodemographic factors that potentially influenced the degree of tetanus immunity were analyzed. Overall, 326 persons were included. Of these, 217 (67%) had never received a toxoid booster, while 109 (33%) had received a booster at least once. Among all participants, 95% had protective tetanus antitoxin levels (> or = 0.11 IU/mL), and 60% had protective antitoxin levels without the need of an immediate booster, i.e. > or = 0.51 IU/mL. Among 70 participants aged > 60 years, 89% had protective antitoxin levels > or = 0.11 IU/mL, and 31% had protective antitoxin levels > or = 0.51 IU/mL. Tetanus antitoxin levels declined with age. Male gender, birth after 1955, and prior receipt of toxoid booster(s) were independently associated with protective tetanus immunity (> or = 0.51 IU/mL) by multivariate analysis. Compared with those without tetanus toxoid boosters, individuals with a prior booster had higher antitoxin levels. The percentage of people with protective immunity declined if the interval between the last toxoid booster increased. Waning immunity to tetanus was observed after primary tetanus vaccination or toxoid booster. The public health policy that one dose of toxoid booster after primary vaccination should be emphasized for continuing protection against tetanus.