Persistence of antibodies after a single dose of Tdap vaccine (tetanus, diphtheria, and 5-component acellular pertussis vaccine) was evaluated in a follow-up study of adolescents (N=324) and adults (N=644) who had received Tdap in earlier clinical trials. Outcome measures were seroprotection (tetanus and diphtheria) or seropositivity (pertussis) and geometric mean concentrations. Humoral immune responses to all antigens were robust 1 month after initial immunization, decreased at subsequent measurements, but continued to exceed pre-immunization levels 1, 3, 5, and 10 years later. Protective levels of diphtheria and tetanus antitoxin persisted in 99.3% of adolescents 10 years after a booster dose of Tdap. Seropositivity to 1 or more pertussis antigens also persisted in most adolescents for 10 years. Although tetanus antitoxin responses were similar in adults to those observed in adolescents, diphtheria antitoxin titers were lower, reflecting the fact that a smaller proportion of adults had received diphtheria toxoid in the previous 10 years compared to adolescents. These data will contribute to the selection of the optimal interval for repeat doses of Tdap.
An understanding of the antibody persistence elicited by a combined tetanus, diphtheria, 5-component acellular pertussis, and inactivated poliovirus vaccine (Tdap-IPV) after adolescent vaccination is important to optimize booster dosing intervals. Our objectives were to compare the safety and immunogenicity of Tdap-IPV coadministered with hepatitis B vaccine (HepB) and sequential administration and evaluate humoral immunity at 3, 5, and 10 years after Tdap-IPV vaccination in adolescents. This phase II randomized, controlled, and open-label study enrolled 280 11-to 14-year-old adolescents with up to 10 years postvaccination follow-up. Group 1 (n ؍ 145) received Tdap-IPV, followed by a HepB dose 1 month later, and group 2 (n ؍ 135) received both vaccines simultaneously. No consistent increases in solicited reactions or unsolicited adverse events occurred with coadministration. All vaccinees attained seroprotective antibody levels at >0.01 IU/ml for diphtheria and tetanus, at a >1:8 dilution for poliovirus (serotypes 1, 2, and 3), and >10 mIU/ml for hepatitis B at 1 month postvaccination. Clinically relevant immunologic interactions did not occur with coadministration. For pertussis, all participants achieved seropositivity levels (at or above the lower limit of quantitation), and 72.7% to 95.8% had 4-fold increases in pertussis antibodies at 1 month postvaccination. At 10 years postvaccination, the remaining participants (62.8% of the original cohort) maintained seroprotective levels of >0.01 IU/ml for diphtheria and tetanus, a >1:8 dilution for all 3 poliovirus serotypes, and 74.1% to 98.2% maintained pertussis seropositivity levels depending on the antigen tested. There were no differences between the groups. These results support the coadministration of Tdap-IPV and HepB to adolescents and suggest that vaccination with Tdap-IPV can offer protection for 10 years after an adolescent booster vaccination. Despite widespread childhood immunization with pertussis vaccines, the recurrence of pertussis has been reported among adolescents and young adults, with periodic outbreaks in several countries, suggesting early waning of immunity (1-8). In these outbreaks, high rates of pertussis infection were observed among infants age Ͻ1 year, and the incidence in adolescents age 10 to 14 years also increased.In addition to pertussis morbidity in infected adolescents and adults, these patients constitute a major source of transmission to infants, especially those Ͻ6 months of age, who are at highest risk for serious disease and death (3, 9). Thus, pertussis immunization of adults and adolescents is recommended for both personal protection and to reduce exposure in vulnerable infants (10, 11). The current recommendations for adolescent vaccination in some European countries and most Canadian provinces include combined tetanus, diphtheria, and acellular pertussis (Tdap) and hepatitis B (HepB) vaccines (12). In Canada, the incidence of reported pertussis decreased in all age groups after the National Advisory Committee on Imm...
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