HEATmarker® VVM – Vaccine Vial Monitors
HEATmarker® VVM time-temperature indicators give visual warning of potentially damaging cumulative heat exposures and indicate to health workers whether a vaccine can be used
Critical to the quality of a vaccine is the cumulative exposure to temperature over time, measured by the Mean Kinetic Temperature (MKT). HEATmarker VVM is a label containing a heat-sensitive material that is affixed to a vaccine vial by the drug manufacturer to allow for full-life heat monitoring. Since the HEATmarker VVM and the vaccine move through the supply chain together, they are exposed to the same conditions and MKT. This allows the HEATmarker VVM to give health workers an overview of the cumulative heat exposure of the vaccine and a clear indication when it has reached its time-temperature end point.
Learn more about Mean Kinetic Temperature (MKT) and pharmaceutical product degradation.
HEATmarker VVM has been used to monitor the temperature exposure of vaccines since 1996, as recommended by the WHO and UNICEF (pdf). Its gradual and permanent color change from light to dark shows the temperature history of the vaccine from the time the VVM is affixed to the vaccine vial by the manufacturer – until the product is used. The inner square of the VVM is made of heat-sensitive material that is initially light in color and 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.
Source: “What is VVM and how does it work?” (pdf) – World Health Organization (WHO).
Since HEATmarker VVM’s appearance changes gradually over time, health workers can use it to easily monitor heat exposure. This helps them preserve valuable inventory by using vaccines that have not yet reached end point and only disposing those that have reached endpoint.
HEATmarker VVMs are available in six categories based on their rate of change at the specified time (days to end point) and temperature profiles (temperature specification):
- very high stability
- high stability
- medium stability
- intermediate stability
- moderate stability
- least stable
Vaccine manufacturers select the appropriate category for their vaccines so that the color change of the HEATmarker VVM is the best match for the heat stability of the vaccine product being monitored.
HEATmarker VVM is a pressure sensitive adhesive label
The manufacturer chooses the HEATmarker VVM that best matches the heat stability of the vaccine after consulting with WHO (Immunization Vaccines and Biologicals) (pdf). This table is used to identify the appropriate category HEATmarker VVM.
|Days to End Point||Shelf Life (years from date of manufacture)||Size|
|Very High||37oC||250||5||10 mm diameter|
|High||37oC||30||5||10 mm diameter|
|Medium||37oC||14||5||10 mm diameter|
|Intermediate||37oC||11||4||10 mm diameter|
|Moderate||37oC||7||4||10 mm diameter|
|Least||37oC||2||4||10 mm diameter|
Accuracy: HEATmarker VVM complies with WHO Specifications WHO/PQS/E006/IN05.4 (pdf)
About MKT – Mean Kinetic Temperature
What is MKT?
Mean Kinetic Temperature (MKT) is a single calculated temperature that expresses the total thermal stress that a product experiences at varying temperatures over time.
The calculation of MKT:
When calculating MKT, higher temperatures receive a greater weight than lower temperatures. As a result, MKT takes into account the accelerated rate of thermal degradation at higher temperatures.
Why does MKT matter?
The manufacturer chooses the HEATmarker VVM that matches the heat stability of the vaccine after consulting with WHO (Immunization Vaccines and Biologicals) (pdf). The table above is used to identify the appropriate category HEATmarker VVM.