[Tetanus antibody levels in healthy people in Henan Province from 2022 to 2023]

Objective: To investigate tetanus antibody levels and distribution characteristics in a healthy population of Henan Province. Methods: A cross-sectional survey was conducted in Henan Province from 2022 to 2023 to investigate the permanent population. Enzyme-linked immunosorbent assay (ELISA) was used to detect anti-tetanus toxoid IgG antibody (anti-TT), and the positive rate (≥0.01 IU/ml), protection rate (≥0.1 IU/ml) and concentration differences of tetanus antibodies in different populations were analyzed. Results: The age M (Q₁, Q₃) of 5 494 participants was 14 (4, 40) years old, with a minimum age of 8 months and a maximum age of 81 years old. The male-to-female ratio was 1.00∶1.18. The total positive rate, protective rate and mean concentration (MC) [M (Q₁, Q₃)] of Anti-TT were 76.48%, 41.72% and 0.067 (0.010, 0.154) IU/ml, respectively. The positive rates of Anti-TT in individuals aged <3, 3-5, 6-9, and 10-14 were 95.32%, 96.05%, 97.81%, and 93.17%, respectively, but gradually decreased with age (χ²_trend=1 283.02, P<0.001). The antibody protection rate [82.13% (579/705)] and MC [M (Q₁, Q₃) of 0.160 (0.122, 0.259) IU/ml] in the population under 3 years old were relatively high, and both showed a decreasing trend with age (protection rate: χ²_trend=1 889.49, P<0.001; MC: t=-54.22, P<0.001). There were significant differences in antibody levels among populations of different ages, regions, occupations, and immunization histories (all P<0.001). Within 13 years after the last dose of TTCV vaccination, the positive rate of Anti-TT was all greater than 90%, but the protection rate and MC continued to decrease with the prolongation of vaccination time (protection rate: χ²_trend=160.58, P<0.001; MC: t=-14.93, P<0.001). After the last dose of vaccination, the protection rate and MC [M (Q₁, Q₃)] decreased to 30.43% and 0.055 (0.036, 0.115) IU/ml, respectively, for 10-13 years. The protection rates of Anti-TT for farmers, workers, people aged 60 and above, and women of childbearing age (20-45 years old) were 7.77%, 22.96%, 8.39%, and 12.72%, respectively. Conclusion: The level of tetanus antibodies in infants and young children in Henan Province is relatively high from 2022 to 2023, but it decreases with age and prolonged post-immunization time. There are significant differences in antibody levels among individuals of different ages, regions, occupations, and immunization histories. Occupational high-risk groups such as farmers and workers, elderly people, and women of childbearing age lack sufficient immunization protection.