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 ≥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 ≤8.6% for any erythema, ≤6% for erythema >10 mm, ≤10.3% for any swelling, ≤6.9% for swelling >10 mm, ≤5.2% for any pain and ≤3.7% for moderate/severe pain.
Conclusion: 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 ≥18 months since a previous TD/Td vaccine.
From the Departments of *Pediatrics, †Microbiology and Immunology, and ‡Mathematics and Statistics, Dalhousie University, Halifax, Nova Scotia, Canada; the §Department of Health and Social Services, Charlottetown, Prince Edward Island, Canada; ∥sanofi pasteur, Toronto, Ontario, Canada; and ¶sanofi pasteur, Swiftwater, PA
Accepted for publication October 28, 2005.
Supported by sanofi pasteur and performed as a partnership between the Clinical Trials Research Center at Dalhousie University and the IWK Health Centre, and the Prince Edward Island Department of Health and Social Services. Dr Halperin has received grant support from the manufacturer of the vaccine, sanofi pasteur, and serves on the advisory board for the company.
Address for reprints: Scott A. Halperin, MD, Clinical Trials Research Center, Dalhousie University, IWK Health Centre, 5850/5890 University Avenue, Halifax, Nova Scotia, Canada B3K 6R8. Fax 1-902-470-7232; E-mail firstname.lastname@example.org.