Reduced-antigen, combined diphtheria, tetanus and acellular pertussis vaccine, adsorbed (Boostrix®): a review of its properties and use as a single-dose booster immunization.

Reduced-antigen, combined diphtheria, tetanus and three-component acellular pertussis vaccine (Tdap; Boostrix®) is indicated for booster vaccination against diphtheria, tetanus and pertussis in individuals from age four years onwards in Europe and from age 10 years onwards in the US. Compared with infant formulations used for primary vaccination, Tdap contains reduced quantities (10-50%) of all toxoids and antigens, which are adsorbed to either ≤0.39 mg/dose (US licensed formulation) or 0.5 mg/dose (rest-of-world formulation) of aluminium adjuvant. The reduced antigen content is designed to avoid the increasing reactogenicity historically seen with the fourth and fifth doses of infant vaccine. This article reviews the immunogenicity, protective efficacy and reactogenicity of Tdap booster administered to children, adolescents and adults, including those aged ≥65 years. In clinical trials, a single booster dose of Tdap induced seroprotective levels of antibodies to diphtheria and tetanus toxoids in virtually all children and adolescents, and in a high proportion of adults and elderly individuals at approximately 1 month post-vaccination irrespective of their vaccination history. In all age groups, seropositivity rates for antibodies against pertussis antigens were ≥90% (including in unvaccinated adolescents), and booster response rates were high. Tdap was safely co-administered with other common vaccines without significantly affecting the immune responses. The immunogenicity and reactogenicity profiles of booster doses of Tdap were generally similar to those of infant diphtheria-tetanus-whole-cell pertussis vaccine and infant diphtheria-tetanus-acellular pertussis vaccine in children aged 4-6 years, and infant diphtheria-tetanus vaccine in older children. In adolescents and adults, the immunogenicity and reactogenicity of Tdap were generally similar to those of reduced-antigen diphtheria-tetanus vaccine, reduced-antigen diphtheria-tetanus-five-component acellular pertussis vaccine and reduced-antigen acellular pertussis vaccine. Therefore, Tdap is suitable as a booster in place of these vaccines, including tetanus toxoid vaccine in the management of tetanus-prone wounds in adults. The quantity of aluminium adjuvant in Tdap did not markedly affect the immunogenicity or reactogenicity of the vaccine. Seropositivity rates for antibodies against pertussis toxin had begun to decline by 5 years after a booster dose of Tdap in adolescents/adults, and a subsequent booster dose 10 years later was generally as immunogenic as the initial booster and was well tolerated. Tdap was safe and well tolerated in all age groups. Local injection-site reactions were the most common adverse events. Most adverse events were of mild or moderate intensity and transient; there were few serious vaccination-related adverse events. Thus, Tdap is highly immunogenic, with low reactogenicity, in all age groups and appears suitable for targeted and/or repeat Tdap boosters in children, adolescents, adults and elderly individuals as part of immunization strategies that may prove beneficial in further limiting the burden of pertussis.