Investigators compared the immunogenicity and reactogenicity of booster doses of a tetanus-diphtheria 5-component acellular pertussis vaccine (Tdap) against those measures of efficacy of tetanus and diphtheria vaccines (Td) in adolescents and adults. The trial, conducted at 39 clinical centers in the United States, included nearly 4,500 participants between 11 and 64 years of age who received either Tdap or Td. The Tdap and Td groups (both adolescents and adults) had a similarly high seroprotection rate (at least 0.1 IU/mL), booster response rate, and one-month antibody titer for tetanus and diphtheria. The incidence of local and systemic reactions and adverse events also was similar in the Tdap and Td groups; adolescents experienced injection site pain slightly more often with Tdap than with Td.
The study also assessed the pertussis antibody response to Tdap by comparing antibody levels with those elicited in 7-month-old infants who received an analogous pediatric diphtheria-tetanus 5-component acellular pertussis vaccine (DTaP) at 2, 4, and 6 months of age. In adults and adolescents, the pertussis antibody titer after one dose of Tdap was, on average, substantially higher than the titer among infants after three doses of DTaP (Pichichero MF et al: JAMA 2005;293:3003).