From November 30 to December 12, 2015, France hosted the 21st Conference of the Parties (COP21) on climate change. The conference was held primarily at the Paris-Le Bourget Exhibition Center in the Seine-Saint-Denis department. The COP21 mission required that every instance of medical care provided under the health care system (established based on UN specifications) be recorded and that the interventions of the medical teams be traceable. Healthcare coverage combined an emergency medical response system (SAMU and SMUR) with a contingency response plan. The Île-de-France Regional Health Agency requested that the Île-de-France Regional Intervention Unit (Cire) conduct daily analyses of the interventions handled and assess the conference’s impact on healthcare and emergency response services. Health monitoring was conducted using a single information system that tracked both the activity of first responders and SAMU units at the COP21 site. This system identified 1,238 visits (mostly for minor issues) involving 1,102 patients, and 34 medical transports were reported. While health monitoring helps identify high-risk situations or those requiring intervention, the event-specific care protocols placed a significant data-collection burden on first responders and the SAMU. The expected objectives of a shared information system for first responders and emergency physicians must be clarified in light of the reasons for seeking care typically observed.