Age-Related Dynamics in Post-Vaccine Antibody Immune Response to Diphtheria and Tetanus Toxoid in Bulgarian Subjects

Abstract

In this study, we investigated the age-related dynamics in post-vaccine humoral immunity to diphtheria (DT) and tetanus (TT) toxoids in the Bulgarian population. In addition, we attempted to correlate the titers of specific antibodies with the predisposition to more common infectious pathology among our study participants. The 208 individuals tested were divided into five age groups: 0-4, 4-6, 6-12, 12-17 and 17-66 years, based on the vaccines received according to the immunization schedule in Bulgaria. Vaccine response was determined by measuring the concentrations of specific IgG antibodies using commercial ELISA kits. Sufficient protective levels of diphtheria (> 0.1 IU/mL) and tetanus (> 0.15 IU/mL) antitoxin were detected in 63.5% and 85.1% of all subjects, respectively. The highest rates of protection against both TT (94.3%) and DT (79.2%) were observed in the youngest age group (0-4 years). We also observed a relatively high rate of insufficient protection (< 0.1 IU/ml) against diphtheria (36% of individuals tested across all age groups) in comparison to tetanus (14.9% of all subjects). The rate of insufficient protection against both antigens was higher among children with frequent infections. Moreover, 77.1% of the individuals having low antibody titers against the highly immunogenic tetanus toxoid, also had low levels of diphtheria antibodies. The level of seroprotection is better for tetanus than for diphtheria toxoid at any age. In conclusion, our data provide information on the level of immunity to diphtheria and tetanus among vaccinated individuals in Bulgaria and allows for the identification of persons suspected of having an immune deficiency. Additional investigations are needed in order to provide reliable recommendations for the national vaccine program and personalized vaccinations.

Keywords

• diphtheria
• tetanus
• vaccination
• seropositivity
• bulgaria