The Effect of Tetanus Toxoid Carrier Protein on Tetanus Antibody Levels and Persistence

Objective To investigate the effect of tetanus toxoid (TT) as a carrier protein on the levels and persistence of tetanus antibodies in children.Method A survey was conducted on 11-13 year old children born between 2010 and 2012 who had received 5 doses of Tetanus Containing Vaccines (TCVs). According to their Hemophilus influenzae type b-TT (Hib-TT) immunization records during infancy, they were divided into a control group, group A, and group B. Blood sample was collected and serum tetanus IgG antibody concentration was detected using Enzyme Linked Immunosorbent Assay (ELISA). The differences in Geometric Median Concentrations (GMCs), tetanus antibody positive rate, and seroprotection rates across different groups were compared.Results Among 364 children investigated, 5-7 years after the last dose of TCVs vaccine, positive rates of tetanus IgG antibodies in the control group, group A, and group B were 95.38%, 96.60%, and 94.34% respectively, with no statistically significant difference. Seroprotection rates were 42.68% in group A ( χ 2 =11.75, P<0.001) and 37.50% in group B ( χ 2 =9.03, P=0.003), with statistically significant differences comparing with 21.23% in control group. Multivariable analysis indicated that compared with children in the control group, children in groups A and B were more likely to have antibodies above the seroprotecting level (OR=2.51, P=0.003 for group A vs. control group; OR=2.31, P=0.002 for group B vs. control group). In addition, compared with female children, male children were more likely to reach the seroprotective level (OR=1.75，P=0.016).Conclusion TT as carrier protein may exert a positive impact on the immune level and persistence of tetanus IgG antibodies. It is suggested to conduct more comprehensive and systematic studies on the role of TT carrier protein-conjugated vaccines in the tetanus immunogenicity in the future, to further explore the potential value of conjugate vaccines and provide more references for optimizing tetanus immune strategies.