title: How soon after a prior tetanus-diphtheria vaccination can one give adult formulation tetanus-diphtheria-acellular pertussis vaccine?
abstract: BACKGROUND
  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 provided by 5931 (84.7%). No whole limb swelling, Arthus-like reactions or serious adverse events related to vaccination were reported. No differences in reports of fever were found by interval since last immunization. Injection site erythema and swelling were slightly and statistically significantly increased among those participants with most recent prior TD/Td. Compared with the 10-year interval group, the maximum increase for any other group was < or = 8.6% for any erythema, < or = 6% for erythema > 10 mm, < or = 10.3% for any swelling, < or = 6.9% for swelling > 10 mm, < or = 5.2% for any pain and < or = 3.7% for moderate/severe pain.
  
  
  CONCLUSIONS
  Although there is a slight increase in injection site events with decreasing interval since a previous immunization, Tdap can be safely administered at intervals of > or = 18 months since a previous TD/Td vaccine.
authors.affiliation: Department of Pediatrics, Dalhousie University, Halifax, Nova Scotia, Canada. scott.halperin@dal.ca
authors.forename: Scott A
authors.initials: SA
authors.lastname: Halperin
authors.forename: Lamont
authors.initials: L
authors.lastname: Sweet
authors.forename: Darlene
authors.initials: D
authors.lastname: Baxendale
authors.forename: Anne
authors.initials: A
authors.lastname: Neatby
authors.forename: Petra
authors.initials: P
authors.lastname: Rykers
authors.forename: Bruce
authors.initials: B
authors.lastname: Smith
authors.forename: Mitchell
authors.initials: M
authors.lastname: Zelman
authors.forename: Diane
authors.initials: D
authors.lastname: Maus
authors.forename: Pierre
authors.initials: P
authors.lastname: Lavigne
authors.forename: Michael D
authors.initials: MD
authors.lastname: Decker
mesh_terms: D000328:Adult; D002626:Chemistry, Pharmaceutical; D002648:Child; D002675:Child, Preschool; D004165:Diphtheria / Q000517:prevention & control; D022422:Diphtheria-Tetanus Vaccine / Q000008:administration & dosage*; D022681:Diphtheria-Tetanus-acellular Pertussis Vaccines / Q000008:administration & dosage* / Q000009:adverse effects* / Q000737:chemistry; D006801:Humans; D007115:Immunization Schedule; D007117:Immunization, Secondary / Q000379:methods*; D007223:Infant; D013742:Tetanus / Q000517:prevention & control; D013997:Time Factors; D014611:Vaccination; D014917:Whooping Cough / Q000517:prevention & control
chemical_list: D022422:Diphtheria-Tetanus Vaccine; D022681:Diphtheria-Tetanus-acellular Pertussis Vaccines