Analysis on diphtheria and tetanus antibody levels and related distributions in healthy population in an area in Sichuan, 2022

Objective To understand the diphtheria and tetanus antibody levels, influencing factors and related spatial distributions in healthy population in an area Sichuan province in 2022.

Methods Using the multi-stage sampling method, a total of 11 surveillance points were selected according to the geographical location of the area, and a total of 440 local residents were selected from 10 age groups in health population. Multivariate logistic regression and spatial autocorrelation were used to analyze the influencing factors and spatial distribution of antibody level.

Results The IgG positive rate was 72.05% for diphtheria and 56.36% for tetanus, and the geometric mean antibody concentration（GMC） was 0.56 IU/mL for diphtheria and 0.47 IU/mL for tetanus. The IgG positive rate ranged from 43.18% (50–59 years) to 90.91% (<1 year) for diphtheria (χ²=63.768, P<0.001) and from 13.64% (>60 years) to 93.18% (<1 year) for tetanus (χ²=190.134, P<0.001). The spatial analysis model showed that the IgG positive rate of diphtheria was significant, and local autocorrelation results showed that diphtheria antibody positive rate, GMC level and tetanus GMC level had three high-low clustering areas, one low-low clustering area and one low-high clustering area. Multivariate Logistic regression models showed that the effects of being man, being immunized, and age <40 years were protective factors for diphtheria antibody level. Being immunized, age <40 years were protective factors for tetanus antibody level.

Conclusion The diphtheria and tetanus antibody levels in healthy population in this area were low. It is suggested to conduct additional immunization of diphtheria-tetanus (DT）vaccine and tetanus vaccine in adolescents, adults and township population to improve the DTP antibody level in whole population.