Decennial administration in young adults of a reduced-antigen content diphtheria,tetanus, acellular pertussis vaccine containing two different concentrations of aluminium

BackgroundRegular booster vaccination might be necessary throughout life to protect against pertussis infection. Nevertheless the duration of protection after booster vaccination remains unclear. In this study, antibody persistence up to 10 years after previous vaccination of adolescents (N = 478) with combined reduced-antigen-content diphtheria-tetanus-acellular pertussis vaccine (dTpa, Boostrix™, GlaxoSmithKline Belgium) containing 0.5 mg, 0.3 mg or 0.133 mg of aluminium was assessed. The immunogenicity, reactogenicity and safety of a decennial booster dTpa dose were also investigated.MethodsYoung adults vaccinated as adolescents in the initial booster study were invited to participate in an assessment of antibody persistence at years 8.5 and 10, and to receive a dTpa booster dose at year 10 with immunogenicity assessment one month later. Those who originally received the 0.5 mg or 0.3 mg formulations received the same vaccine at year 10. Those in the 0.133 mg group received the 0.5 mg formulation. Reactogenicity and safety endpoints were captured until 30 days after booster vaccination.ResultsPrior to the decennial booster at year 8.5 and year 10, all participants had seroprotective antibodies for diphtheria (ELISA or neutralisation assay) and tetanus. At least 77.8% were seropositive for anti-pertussis toxin (PT) antibodies at year 8.5 and 82.8% at year 10. All participants were seropositive for antibodies for filamentous haemagglutinin and pertactin at both time points. The decennial booster dose induced robust increases in antibody GMCs to all antigens. The post-booster anti-PT geometric mean concentration was 82.5 EL.U/ml (95%CI 67.0–101.6) and 124.0 (103.5–148.5) in the 0.3 mg and 0.5 mg groups, respectively. The reactogenicity and safety profile of the decennial booster dose was consistent with the known safety profile of dTpa. No serious adverse events were reported.ConclusionsDecennial booster vaccination with either of the two licensed formulations of dTpa was highly immunogenic and well tolerated in young adults. Either formulation could be confidently used as a decennial booster.This study is registered at www.clinicaltrials.gov NCT01147900