Needle temperature effect on pain ratings after injection

Objectives: Little research regarding appropriate immunization administration technique for adults has been carried out. Pain is a leading cause of self-deferral from immunizations. The purpose of this study was to determine whether administering intramuscular injections using cold needles would decrease patients' perceived pain and have an effect on the immune response elicited by the vaccine. Methods: Eighty participants received an injection of influenza vaccine in 1 arm and a saline injection in the other using a cold or room temperature needle in a double-blind fashion assigned at random. Participants rated their pain after each injection using a standard visual pain scale bounded by no pain and most painful injection ever. Vaccine antibody response was measured using hemagglutination inhibition assays. Results: Overall, pain scores after influenza vaccine administration were quite low (34.2 +/- 2.5 mm). The mean pain score for influenza vaccine was not different using cold or room temperature needles (cold 32.2 min +/- 3.20 vs. room temperature 36.0 mm +/- 3.80; t = 0.76; P = 0.450). The mean pain scores for saline injections did not differ (room temperature 23.7 mm +/- 3.19 vs. cold 25.2 +/- 2.95; t = -0.34; P = 0.73). Individuals receiving injections with cold needles had less bruising (0/40 vs. 5/40; P < 0.02) at the injection site, but incidences of pain and erythema were similar. The use of cold needles for vaccine administration had no effect on antibody response. Conclusions: Pain after influenza vaccine administration is generally mild. Use of cold needles may not be worth pursuing for injections associated with mild pain. However, it may be worthwhile to explore using cold needles as an analgesic with more painful injections.