Monitor the Cumulative Temperature Exposure of Vaccines
Since 1996, HEATmarker® Vaccine Vial Monitors (VVM), manufactured by Temptime®, have been used to monitor the temperature exposure of vaccines, as recommended by the WHO and UNICEF. In 2012, WHO determined VVM to be a "critical characteristic", a required element of all vaccine tenders submitted to UNICEF.
HEATmarker VVM and VVM+ indicators are affixed to a vaccine vial by the manufacturer to allow for full-life temperature monitoring. The inner square features a heat-sensitive material that becomes darker when exposed to heat. The color change is faster at higher temperatures and slower at lower temperatures. At the end point, the inner square is the same color as or darker than the outer circle. This allows the HEATmarker VVM to give health workers an overview of the cumulative heat exposure of the vaccine and a clear visual indication when it has reached its time-temperature end point, informing them whether the vaccine should be administered.
