In Great Britain, it is recommended that physicians administer routine immunizations by deep subcutaneous or intramuscular injection using a 25- or 23-gauge needle. Needle length is not mentioned in those recommendations, but anecdotal evidence indicates that shorter needles are associated with fewer adverse reactions. Diggle and Deeks conducted a randomized, controlled trial to determine if needle length affects the incidence of redness, swelling and tenderness in pediatric immunizations.

Eight general practices participated in the study. Infants who were scheduled to receive their third primary immunization and had no contraindications were randomly assigned to immunization with a 25-gauge, 16-mm needle or a 23-gauge, 25-mm needle. Nurses in the participating practices were verbally instructed to use standard techniques of injection. Parents recorded redness, swelling and tenderness for three days following injection and returned the results by mail.

Six hours after injection, the parents of 60 percent of the 57 infants injected with the 25-gauge, 16-mm needle reported redness, compared with 40 percent of the 53 infants injected with the 23-gauge, 25-mm needle. At three days after injection, redness was still reported by 28 percent of the 25-gauge, 16-mm group compared with 4 percent of those injected with the 23-gauge, 25-mm needle. Swelling was also common in both groups but reduced in the 23-gauge, 25-mm needle group. At six hours, swelling occurred in 58 percent of the 25-gauge, 16-mm infants compared with 23 percent of the 23-gauge, 25-mm group. Swelling persisted at least three days in 40 and 13 percent of the infants, respectively. Tenderness at the injection site was initially present in 28 and 17 percent of the groups but was gone by the third day, with the exception of one child in the 25-gauge, 16-mm group (see accompanying table).

The authors conclude that use of the longer 23-gauge, 25-mm needle was associated with significant reduction in redness and swelling following routine pediatric immunization. This may be due to vaccine reaching appropriate levels more consistently with the longer needle. Results from previous studies have shown that the depth of the injection, rather than the gauge of the needle, is associated with reaction frequency. The authors calculate that use of the longer needle would prevent one infant from experiencing a local reaction for every five infants who were immunized.

editor's note: Busy family physicians frequently perceive “research” as an inappropriate and impractical concept in their office. This study illustrates “organized curiosity” at its best—a simple observation, validated by a credible study, leading to valid results that could improve practice. The change may be modest and is not likely to be noticed by the wider world of medical research. Infants, their families and their primary care professionals will appreciate avoiding those minor symptoms. Cumulatively, the impact on health services in calls and treatments avoided could be highly significant. What other modest improvements in routine activities could we make to benefit our patients and the health care process?—A.D.W.