POST 00978E : VVM USE AND FREEZE INDICATORS

POST 00978E : VVM USE AND FREEZE INDICATORS Follow-up on Posts 00960E, 00962E, 00964E, 00970E, 00973E and 00975E 22 September 2006 _____________________________________ This posting contains two contributions. The first is from Jibrin Garba ([log in to unmask]" eudora="autourl">mailto:[email protected]) from Nigeria who asks about an improved Freeze-Watch. The second is an extensive contribution from Ãœmit Kartoglu ([log in to unmask]" eudora="autourl">mailto:[email protected]) from WHO/Geneva. He provides detailed information about VVMs that many will find good to revise, or learn. He also discusses the concept of a vial freeze indicator, thus answering Jibrin's question. _____________________________________ I will want to suggest that this could be possible if the persons behind the manufacturing of the Freeze-Watch can improve on it to withstand less than minus zero C. I think it might give us the solution to shake test. As all liquid vaccines contained in the refrigerator were such freeze-watched, it could be certain that such vaccines have frozen without any need for a shake test. Please contact the Freeze-Watch manufacturer, and please let me know if that is possible. Yours sincerely, Jibrin Garba, Katsina State SIO, Nigeria ------------------------------------- With the new reorganization in the WHO, it is Quality, Safety and Standards (QSS) team that is responsible for issues relating to Vaccine Vial Monitors (VVM). Recent postings on VVM USE urged us to make a briefing note for clarity as for as responding to some specific queries. VVM TYPES First I would like to start with a complaint QSS received some months ago. The claim was that VVM on MR vaccine is not changing color despite being kept at room temperature for some days. We have completed the investigation and found no evidence that VVMs do not change color. Our conclusion was misinterpretation of VVM reading in the field. The MR vial with VVM was kept outside the cold chain at a room temperature (assuming it is around 20 degree C) for about 9 days. This particular vaccine had a VVM14 type. VVM14 can stand constant room temperature for more than 6 months. This means that the change that occurs in 9 days at room temperature (which falls down during evenings) may not be seen with the naked eye. Vaccine vial monitors 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. 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. WHO identifies four category of vaccines: VVM30 high stability vaccines VVM14 medium stability vaccines VVM7 moderate stability vaccines VVM2 least stable vaccines The nomenclature of VVM categorization corresponds to thermostability data of vaccines at 37 ° C. This means vaccines that are attached with the 30 model VVM are thermostable for at least 30 days at constant 37 ° C. A much longer period of time is needed to reach the end-point in VVM if kept at lower temperatures. For example, VVM14 kept at room temperature (20 ° C) will reach its discard point in 196 days (6.55 months). Therefore, as in the above mentioned complaint, it is not possible to see the color change that occurred in 9 days at room temperature. Such changes can only be confirmed by a special color reflection densitometer (Xrite Model 404 GS or GSX). At room temperature, it will take 421 days (14 months) for VVM30 to reach its discard point. As for VVM2 (oral polio vaccines) discard point will be reached in 23 days. This shows that the reaction rates vary from category to category. Most people in the field are experienced with OPV VVMs, however, they should not take OPV VVM as a proxy to compare others that do not change color as the OPV VVM does. In the above complaint, VVM14 behaves seven times slower than OPV VVM. We were always asked to give the list of vaccines and the corresponding types of VVMs. This table cannot be produced for a very simple reason. During the prequalification assessment of vaccines, stability data is analyzed and based on the data a type of VVM from the above list (2, 7, 14 or 30) is assigned to this specific vaccine. Although in general the same vaccine from different manufacturers falls in the same category, there are some exceptions. For example most of the BCG products have VVM30, except one that is with VVM14. Measles is another example, some measles products are with VVM7 while some are with VVM14. However, all OPV takes VVM2. In summary, no matter what type of VVM is attached on the vial, all VVMs work in the same way but at different reaction rates. This is why, for example a VVM on OPV cannot be used as a proxy for other vaccines. In the 5 August TechNet21 e-Forum Post00960E, Anton Widjaya ([log in to unmask]" eudora="autourl">mailto:[log in to unmask]) and Vanda Moniaga ([log in to unmask]" eudora="autourl">mailto:[log in to unmask]) explained that OPV was discarded based on VVM readings (reached and beyond discard point) and BCG was discarded mainly for not having a VVM. All other vaccines were saved based on VVM readings. This was an excellent example of explaining why not to use one type of VVM as a proxy for others. As for detailed information on the temperature sensitivity of vaccines, I would also like to announce that the renown WHO manual "Thermostability of vaccines (A. Galazka, J. Milstien and M. Zaffran, WHO/GPV/98.07)" is now being rewritten and will be published soon under a new name "Temperature sensitivity of vaccines (J. Milstien, U. Kartoglu and M. Zaffran, WHO/IVB/06.10). As soon as an electronic version of the manual is available on the web, we will also announce this on the TechNet21 e-Forum so readers can check stability information from the most recent source. I also strongly recommend the publication "Getting started with VVMs, WHO/V&B/02.35". This publication provides much practical information on the use of VVMs that appeared during VVM use discussions in TechNet21. This document can be downloaded from the following link: http://www.who.int/vaccines-documents/DocsPDF02/www716.pdf This miracle tool VVM opens a new era in front of the country immunization programmes. As done in several countries, VVM based vaccine management allows immunization programme to reach all its target population regardless how difficult access is. WHY WE DO NOT HAVE A VIAL FREEZE INDICATOR? Vial freeze indicator as a concept exists. This issue was widely discussed with members of the Technology and Operations Panel of WHO on 25 February 2003 in Geneva, where 20 experts from various disciplines, organizations and vaccine manufacturers gathered. It was argued that vial freeze indicator (VFI) would not solve the problem for the following reasons (exactly as it is noted in the minutes of the above mentioned meeting): * It is a separate application to the vaccine label (there is no technology to display in a single unit a cumulative heat exposure history together with single freezing event). * Activation of the VFI does not necessarily mean that vaccine has been frozen. It means that vaccine has been exposed to freezing temperatures. If the vaccine texture is not affected (meaning that it passes the shake test), vaccine can be safely used; and yet in this case, the VFI will give a "frozen" signal (because it is irreversible), which could be very confusing. Such an application would increase vaccine wastage unnecessarily. * More efforts should be spent on "prevention" of freezing rather than relying on "alarm" signals that freezing has happened. * It may not be cost-effective. Participants agreed that the development of vial freeze indicator is not an immediate priority. Hope this clarifies WHO stand point with VFIs. Thanks and cheers, Dr. Umit Kartoglu, Scientist, Quality, Safety and Standards, FCH/IVB/QSS, Room M213, World Health Organization ______________________________________________________________________________ All members of the TechNet21 e-Forum are invited to send comments on any posting or to use the forum to raise a new discussion or request technical information in relation to immunization services. 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