Local thermal reaction after influenza vaccination: Quantification by infrared imaging and biometric considerations.

BACKGROUND: Extensive clinical investigations are mandatory to evaluate the safety and reactogenicity of vaccines. The recording of common adverse events like injection site soreness or general discomfort derives from individual subjective perceptions. Thermal imaging at the injection site possibly provides a non-subjective and a non-invasive approach to supplement this evaluation. RESULTS: A protocol for quantified injection-site infrared imaging included 86 participants during a flu vaccine campaign, 40% of whom had a thermal reaction of 1 °C; 25-30% had no thermal response. There was little subjective pain reporting and no clinical correlations were observed except with post-vaccination erythema. Higher responses were linked with advanced age and multiple previous vaccinations. CONCLUSION: Evan if influenza vaccine was only moderately reactogenic, a thermal response was detectable in about 70% of vaccinees, though no relationship to reactogenicity was seen. Infrared imaging might however be a prospective tool for individual studies of vaccine-induced vascular responses.