Effect of warming adult diphtheria-tetanus vaccine on discomfort after injection: a randomised controlled trial.

OBJECTIVE To determine whether warming or rubbing adult diphtheria tetanus (ADT) vaccine immediately before administration affects its temperature and reduces the incidence of pain. DESIGN Double-blind, randomised controlled trial and in-vitro temperature study. SETTING Emergency department (ED) of a regional hospital between April and December 2001. PATIENTS Convenience sample of 150 patients aged 16 years or over who presented to the ED requiring ADT booster vaccination. INTERVENTION Patients were randomised to receive vaccine that was "cold" (no deliberate warming), "rubbed" between the palms for 1 minute, or "warmed" in a 37 degrees C incubator; vaccine was administered as recommended in Australian guidelines. MAIN OUTCOME MEASURES Incidence of pain and pain score on McGill Present Pain Intensity Questionnaire at 5 minutes, 24 hours and 48 hours after injection; and temperature of vaccine after preparation for simulated administration. RESULTS The "cold" vaccine had significantly lower temperature (mean, 19.1 degrees C; 95% CI, 17.5-20.7 degrees C) than the "warmed" vaccine (mean, 28.9 degrees C; 95% CI, 28.4-29.4 degrees C) and "rubbed" vaccine (mean, 26.9 degrees C; 95% CI, 24.5-29.3 degrees C). There was no significant difference in incidence of pain between the groups who received vaccine prepared in different ways at any follow-up (5 min: P = 0.62; 24 h: P = 0.58; 48 h: P = 0.61) or overall (P = 0.99). Among those who completed follow-up, incidence of pain at any time was 77/138 (56%); there was no difference in their time-averaged pain scores (P = 0.63) or peak pain scores (P = 0.60). CONCLUSIONS Warming or rubbing ADT vaccine does not reduce the incidence of pain after administration. Regardless of how ADT vaccine is prepared, its temperature approaches ambient by the time it is injected.