POST 00564E : COLOR OF VVMs

POST 00564E : COLOR OF VVMs Follow-up to Posts 00558E and 00562E. 8 May 2003 ________________________________________________ Previous postings may have created some confusion as shows the message below from Anthony Battersby (mailto:[log in to unmask]). It is likely that other members also feel the same. Thus mit Kartoglu (mailto:[log in to unmask]) from WHO is providing a detailed clarification (further below) along with another illustration (attached). ________________________________________________ This is all very confusing. In the first posting 558E on 15 April the attachment shows a VVM with 4 stages. The first two stages have no name, the third is called the Discard Point and the last Beyond the Discard Point. The other attachment shows only a VVM "showing no heat exposure", what about time? and no mention of which stage it is at. In the second posting 562E on 26 April there is are two columns of VVMs at various stages of exposure. This has only 3 stages called stage 1 "start point", stage two "mid point" and stage 3 "end point". What happened to stage 4? What is the significance of stage 2? It seems to be entirely arbitrary, why is that exposure any more significant than the one above or below? What is the significance of the maximum and minimum? If it is the range of colour variation between batches then it should be labelled as such. Anthony _______________________________________ 1. "Start color" refers to a VVM at the time of its production showing NO heat exposure. VVM start color of the square is never snow white. It always has a tinge of bluish grey. From then on, until the temperature and/or duration of heat exposure reaches a level known to degrade the vaccine beyond acceptable limits, the inner square remains lighter than the outer circle. 2. At the "discard point", the inner square is the same color as the outer circle. This indicates that the vial has been exposed to an unacceptable level of heat and the vaccine has been 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. 3. The "mid point" refers to an arbitrary stage which falls in the middle of start stage and discard point. This also corresponds to the stage that many people call "second stage". 4. "Beyond discard point" refers to all stages in which the inner square is darker than the outer circle. 5. In reading VVM, the point to focus on is the color of the inner square relative to the color of the outer circle. The rule remains simple: If the inner square is lighter than the outer circle, the vaccine may be used, and if the inner square is the same color or darker than the outer circle, the vaccine must not be used. VVM with a darker square (but has not reached its discard point) must be used prior to vaccines with VVM with a lighter square. This is an important aspect of VVM in helping health workers and store keepers make managerial decisions on vaccine use. 6. VVM also comes in slight different hues from batch to batch (bluish to bluish gray). However, the interpretation of the VVM remains the same regardless of slight changes in hue. The attachment given with the posting 562E (26 April) shows two columns of VVMs at different levels of heat exposure ranging from start color to discard point. The figure shows the variability of VVMs by giving an example of minimum and maximum values in hue. 7. VVM and its status also need to be checked on vaccine arrivals and be recorded in the Vaccine Arrival Report. In an international vaccine transport under normal conditions (that WHO required packaging and shipping requirements are met and no interruptions occur during transport), the temperature exposure history of the shipment is not as extreme to initiate a visible change in VVM status. Under normal conditions, no visible change is expected to happen between vaccine manufacturer and the point of destination. Therefore, it is important to check all aspects of the shipment. 8. I am attaching a new illustration with the hope that it will bring clarification if there is any confusion. This illustration was not prepared to replace the original one explaining how to use VVMs. But if found useful, it can be used in trainings. _____________________________________________________________________________ Visit the TECHNET21 Website at http://www.technet21.org You will find instructions to subscribe, a direct access to archives, links to reference documents and other features. ______________________________________________________________________________ To UNSUBSCRIBE, send a message to : mailto:[log in to unmask] Leave the subject area BLANK In the message body, write unsubscribe TECHNET21E ______________________________________________________________________________ The World Health Organization and UNICEF support TechNet21. The TechNet21 e-Forum is a communication/information tool for generation of ideas on how to improve immunization services. 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