Pertussis is a highly infectious illness that has seen cyclical peaks in frequency and increased outbreaks during the last several decades. The tetanus-diphtheria-acellular pertussis vaccine (Tdap) with reduced antigen content was used to boost individuals aged greater than or equal to 10 years who were previously vaccinated with a diphtheria-tetanus-acellular pertussis vaccine (DTaP) to reduce pertussis morbidity and maintain protection against diphtheria and tetanus throughout adolescence and adulthood. 

A study conducted by researchers was a phase III, open-label, non-randomized, multicenter follow-up trial (NCT01738477) that included 19–30-year-old volunteers from the United States who had had booster immunization 10 years before with either Tdap (Tdap group) or Td (Td group). Tdap vaccine was given to 128 (Tdap group) and 37 (Td group) patients in total. 

All patients were seroprotected against diphtheria and tetanus after receiving Tdap (antibody concentrations 0.1 international units [IU]/ml). Immune responses to a second Tdap dosage in the Td group for diphtheria and tetanus and a 3-dose DTaP vaccination for pertussis antigens were shown to be non-inferior to responses evoked by a first Tdap dose in the Td group (primary objectives). All patients in both groups had antibody concentrations over test cut-offs after booster vaccination, and antibody geometric mean concentrations rose by 3.8–15.5-fold for all antigens compared to pre-booster levels. The Td (80.6%) and Tdap (85.6%) groups had similar rates of adverse events. In young people, a Tdap dosage given after a prior Td or Tdap vaccine was shown to be immunogenic and well-tolerated, supporting Tdap immunization at 10-year intervals.