Use of a 25-mm needle was associated with less risk of redness and pain than was use of a 16-mm needle among children receiving their fifth diphtheria-tetanus-acellular pertussis vaccine, according to results from a prospective randomized trial.
The results also suggested that the thigh should be considered as the site for the fifth injection, the investigators reported.
Dr. Lisa A. Jackson of the epidemiology department of the University of Washington, Seattle, and colleagues reported results from 1,315 pediatric patients (median age 54 months) in a study funded by Sanofi-Pasteur Inc.
Most (1,174 patients) received the vaccination in the arm; 141 were injected in the thigh. Among those injected in the arm, there was a significantly greater proportion with any injection-site redness (76%) among the 381 on whom a 16-mm needle was used than there was among the 793 patients on whom the 25-mm needle was used (65%).
Swelling was also significantly less common among patients injected in the arm with the longer versus the shorter needle (reported in 67% and 55%, respectively), as was pain (61% vs. 53%).
The same trend was seen for each reaction among patients injected in the thigh, but the differences did not reach significance (Pediatrics 2008;121;e646–52).
Relative risks adjusted for age, gender, and body mass index (BMI) showed that the risk for several localized reactions was less when the injection site was the thigh, rather than the arm, especially redness (relative risk 0.63) and swelling (RR 0.53).
“Together these findings suggest that a 16-mm needle should not be used for administration of the fifth DTaP vaccine injections and that vaccination in the thigh is an option that may be considered by parents and providers who would like to decrease the risk of local reactions characterized by redness and swelling,” they wrote, adding that these findings are consistent with those of similar studies in the literature.
Both practices are consistent with guidelines from the American Academy of Pediatrics and the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices, they noted.
The investigators cautioned that neither the needle length nor the injection site was randomized, and that the latter factor seemed to correlate with the size of the child.
However, their analyses did control for BMI. “In analyses restricted to children with a BMI of 14.50 to 16.79 kg/m
Dr. Jackson has served as a consultant to Sanofi Pasteur in the past and is on the speakers' bureau for Sanofi Pasteur.
She has also received research funding from Wyeth Pharmaceuticals, ID Biomedical Corp., GlaxoSmithKline Inc., and Novartis, and has served as a consultant to Wyeth and Novartis.