Reduced-Antigen, Combined Diphtheria, Tetanus and Acellular Pertussis Vaccine, Adsorbed (Boostrix (R)) 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 (R)) 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.
