Study Question: Does warming the adult diphtheria-tetanus vaccine reduce the discomfort of the injection?

Setting: Emergency department

Study Design: Randomized controlled trial (double-blinded)

Synopsis: Many health care professionals warm the adult diphtheria-tetanus vaccine before injection to reduce pain and side effects. In this trial, investigators identified a convenience sample of 150 patients 16 years or older who visited an emergency department for a diphtheria-tetanus booster vaccination.

Participants were randomly assigned in a double-blind fashion (concealed allocation assignment) to receive a vaccine that had been given no deliberate warming (“cold”); rubbed for one minute between a nurse's hands (“rubbed”); or placed in a warming cupboard at 37°C (98.6°F) for five minutes (“warmed”). The temperature of the liquid was measured using a flux wire temperature probe immediately before injection. All outcomes were assessed five minutes after injection and at 24 and 48 hours by persons blinded to treatment group assignment. A total of 92 percent of patients were available for complete follow-up.

Using intention-to-treat analysis, no significant differences were noted in the incidence of pain or the number of adverse reactions after injection of the adult diphtheria-tetanus vaccine injection among the groups at any of the follow-up evaluations. Interestingly, the temperature of the vaccines immediately before injection approached ambient temperature in all three groups, most likely secondary to the large surface area of the syringe relative to the small amount of fluid (0.5 mL). The authors also should have evaluated the pain immediately after injection to see if there was any difference among the groups.

Bottom Line: Warming the adult diphtheria-tetanus vaccine, by rubbing between the hands or with the use of a warmer, does not reduce the incidence of pain or adverse reactions after injection. (Level of Evidence: 1b)