How soon after a prior tetanus-diphtheria vaccination can one give adult formulation tetanus-diphtheria-acellular pertussis vaccine?
GROUND: Adult formulation tetanus and diphtheria toxoids and acellular pertussis vaccines (Tdap) have been developed to prevent pertussis in adolescents and adults. There are concerns that unacceptable rates of severe injection site reactions, including Arthus-type reactions might occur if Tdap is administered too soon after a previous tetanus and diphtheria toxoid-containing vaccine formulated for infants and younger children (TD) or older children and adults (Td). METHODS: To evaluate whether adverse reactions after Tdap might be related to time since last receipt of TD/Td, we performed an open label, province-wide, clinical trial comparing the reactogenicity of Tdap given 18 months-9 years versus > or = 10 years after a previous TD/Td. RESULTS: Seven thousand one hundred fifty-six children and adolescents were enrolled in the study (464-963 subjects per cohort), and 7001 had documented dates of the previous immunization within the specified intervals; adverse event data were provide
