Vaccine Vial Monitor

A Vaccine Vial Monitor (VVM) is a label containing a heat-sensitive material which is placed on a vaccine vial to register cumulative heat exposure over time.

The VVM is a circle with a small square inside it. It can be printed on a product label, attached to the cap of a vaccine vial or tube, or attached to the neck of an ampoule.

The combined effects of time and temperature cause the inner square of the VVM to darken, gradually and irreversibly. A direct relationship exists between the rate of color change and temperature:

1. The lower the temperature, the slower the color change.
2. The higher the temperature, the faster the color change.

Vaccine Vial Monitor
Showing no heat exposure

The inner square of the VVM is made of heat sensitive material that is light at the starting point and becomes darker with exposure to heat.

VVM is the only tool among all time temperature indicators that is available at any time in the process of distribution and at the time a vaccine is administered indicating whether the vaccine has been exposed to a combination of excessive heat over time and whether it is likely to have been damaged. It clearly indicates to health workers whether a vaccine can be used.

Reading the Stages of the VVM

The point to focus on is the color of the inner square relative to the color of the outer circle:

1. Rule 1: If the inner square is lighter than the outer circle. If the expiry date has not been passed, the vaccine may be used.
2. Rule 2: If the inner square is the same color as, or darker than, the outer circle, the vaccine must not be used.

Figure explains the interpretation of VVM

VVM color change is a continuous process. The combined effects of time and temperature cause the inner square (active surface) of the VVM to darken gradually and irreversibly. The rate of color change increases with temperature.