Antibody persistence 2 and 3 years after booster vaccination of adolescents with recombinant acellular pertussis monovalent aP(gen) or combined TdaP(gen) vaccines

BACKGROUND: Recombinant pertussis vaccines inducing long-lasting immune responses could help to control the rise in pertussis. We here report on persisting antibody responses 2 and 3 years after booster vaccination with a new generation recombinant acellular pertussis vaccine. METHODS: Participants of a phase 2/3 randomised-controlled clinical trial with a monovalent pertussis vaccine containing genetically inactivated pertussis toxin (aP(gen)) or its tetanus and diphtheria toxoids combination (TdaP(gen)), or a chemically detoxified comparator vaccine (Tdap(chem)), (originally conducted between July and August 2015) were invited to participate in observational studies of persisting antibody responses 2 and 3 years after vaccination. Serum IgG against pertussis toxin (PT-IgG) and filamentous hemagglutinin (FHA-IgG) were assessed by ELISA, and PT-neutralising antibodies (PT-Nab) by Chinese Hamster Ovary cell assay. FINDINGS: Waning of antibodies stabilised in aP(gen) and TdaP(gen) vaccinees 2 and 3 years after vaccination. Three years post-vaccination PT-neutralising antibodies remained 4·6-fold (95% Confidence Interval (CI) 2·6–8·1) and 3·7-fold (95% CI 2·2–6·1) higher, PT-IgG antibodies 3·0-fold (95% CI 2·2–4·1) and 2·5-fold (95% CI 1·9–3·3) higher, and FHA-IgG antibodies 1·8-fold (95% CI 1·3–2·5) and 1·6-fold (95% CI 1·2–2·1) higher than baseline in aP(gen) and TdaP(gen) recipients, respectively. In the Tdap(chem) group, PT-neutralising and PT-IgG and FHA-IgG antibodies were back at baseline levels 2 years post-vaccination. Three years post-vaccination seroconversion rates for PT-neutralising antibodies were 65·0% (95% CI 44·1–85·9) and 55·0% (95% CI 33·2–76·8) in aP(gen) and TdaP(gen) recipients, respectively. INTERPRETATION: Considering the persistence of elevated antibody responses 3 years post-booster vaccination, genetically detoxified monovalent aP(gen) and TdaP(gen) vaccines can be expected to induce longer-lasting protection than chemically inactivated Tdap vaccines. FUNDING: BioNet-Asia