Comparison of Different Analgesic Methods for Reducing Pain From Adult Intramuscular Influenza Virus Vaccine Injection

In this study, we will compare relative effectiveness of 4 analgesic strategies (i.e., topical local anesthetics, vapocoolant spray, tactile stimulation and distraction) in adults undergoing routine immunization in order to provide further evidence of the effectiveness of each intervention and to determine if one method is superior to another. We are not including a 'no treatment' group because we do not wish to subject participants to unnecessary pain when there are available analgesic treatments. Moreover, in the presence of a 'no treatment' group, we cannot rule out a placebo effect for all treatment groups unless we provide a matched placebo for each intervention, which is not feasible. In future studies, we plan to address the added benefit of combining analgesic interventions (i.e., evaluating the effect of a multimodal approach).