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Objective: To evaluate immunogenicity and reactogenicity of primary vaccination with reduced-antigen-content diphtheria-tetanus-acellular pertussis (dTpa) or dTpa-inactivated poliovirus (dTpa-IPV) vaccine compared to diphtheria-tetanus-toxoid vaccines (Td) in adults ≥ 40 years of age without diphtheria or tetanus vaccination for 20 years or with an unknown vaccination history.Research design and methods: Double-blind, randomized, controlled clinical trial. Primary vaccination with either three doses of dTpa, one dose of dTpa-IPV followed by two doses of Td, or three doses of Td vaccine (control) administered in a 0-1-6-month schedule.Main outcome measures: Blood samples were collected before commencement and 1 month after each dose. Local and general symptoms were solicited for 15 days after each dose.Results: A total of 460 adults were enrolled, of whom over 48% did not have protective antibody concentrations against diphtheria and tetanus. One month after dose 3 > 99% had seroprotective anti-diphtheria and tetanus antibodies. Three doses were required to maximize anti-diphtheria seroprotection rates. A vaccine response to pertussis antigens was observed in > 92% of dTpa and dTpa-IPV recipients after dose 1. One month after dTpa-IPV, > 98.4% had seroprotective anti-polio titres. No statistically significant differences in local or general symptoms between groups were observed.Conclusions: dTpa and dTpa-IPV can provide primary vaccination of adults. Combinations of dTpa or dTpa-IPV can be used to replace Td and provide booster vaccination against pertussis and polio simultaneously with diphtheria and tetanus, even in situations where the primary vaccination history is unknown. [ABSTRACT FROM AUTHOR]