Earth quakes occur often in Indonesia, since it falls under the seismic zone. Once there was a big earth quake and there was no power for many days. Due to the unavailability of power, vaccines stored in refrigerator could not be assessed, whether those vaccines can be used or not. So, all the vaccines were thrown away and not used assuming that the vaccines were not fit to use. Here comes the VVM, which helps!! VVM will play an important role during these times, since Corona Vaccines are widely used in the world during this Pandemic time.
What is a VVM?
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 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 colour change and temperature.
The lower the temperature, the slower the colour change.
The higher the temperature, the faster the colour change.
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.
History
The concept of VVM’s was started by World Health Organization [WHO] in 1979 and the first vaccine tested using a VVM was the measles vaccine.
Purpose of VVM
Vaccines must be maintained at controlled temperatures to remain effective. But often, vaccination campaigns are conducted in extremely hot weather conditions. So how can it be ensured that the vaccine being delivered has not been exposed to heat that could cause damage? That is where the VVM comes in!
VVM change colour when the vaccine is exposed to heat over time. And so, this little label affixed allows health workers to know that the vaccine has not been exposed to excessive heat.
Vaccine vial monitors [VVM] serve primarily to warn health workers when the cumulative heat exposure of a vial of vaccine has exceeded a pre-set limit, beyond which the vaccine should not be used. In addition, changes in the appearance of the VVM before this limit is reached will serve to guide health workers to first use more exposed vials of vaccine.
Mechanism of action
VVM colour change is a continuous process. The combined effects of time and temperature cause the inner square of the VVM to darken gradually and irreversibly. 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. At the starting point, the inner square is a lighter colour than the outer circle. From then on, until the temperature and/or duration of heat reaches a level known to degrade the vaccine beyond acceptable limits, the inner square remains lighter than the outer circle. At the discard point, the inner square is the same colour as the outer circle. This reflects that the vial has been exposed to an unacceptable level of heat and the vaccine degraded beyond acceptable limits. The inner square will continue to darken with heat exposure until it is much darker than the outer circle. Whenever the inner square matches or is darker than the outer circle, the vial must be discarded.
Rule 1: If the inner square is lighter than the outer circle, the vaccine may be used.
Rule 2: If the inner square is the same colour as, or darker than, the outer circle, the vaccine must not be used.
Types of VVM
There are four different types of VVMs designed for different types of vaccines depending on their heat stability. Reaction rates are specific to four different models of VVM, relating to four groups of vaccines according to their heat stability at two specific temperature points. The labels are selected based on the stability study of the Vaccines.
Uses
It helps in many ways!!. WHO and UNICEF urge to use VVM’s in Vaccine labels.
1.Ensuring the vaccines administered have not been damaged by heat.
2.Reducing vaccine wastage.
3.Highlighting cold chain problems.
4.Managing vaccine stocks.
Bottom line
Unfortunately, the health workers are not trained for the importance / purpose of these VVM’s in vaccine vials. Training the health workers becomes the prime challenge in the successful implementation. Hope this blog will help someone, somewhere in the world about VVM during this pandemic time.
Note-The images given for representation in this blog are taken from Google Images. Many thanks for Google.
Very informative, does this VVM is mandatory for vaccines and can it be inbuilt inside labels as many critical medicines are thrown away due to short exposure to higher temperatures?
Thank you Jignesh. VVM is not mandatory but highly recommended. Can be explored further!