mardi 10 juin 2008
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POST 01277E: VVM—A WHO-PREQUALIFIED AND VALIDATED TOOL FOLLOW-UP ON POSTS: 01264E, 01266E, 01275E 10 JUNE 2008 ******************************************* The query regarding VVM reliability has generated a fair number of responses--a few heated ones too. An interesting diversion here before we take the bull by its horns: the VVM is older than the TechNet e-forum (used on UNICEF-supplied OPV vials since 1996). For those of you who have an historical bent of mind, a chronological detail to share: the TechNet e-forum was originally the VVM forum. In June 1998, it became the TechNet forum (and had 145 members). Now to come to the point. The VVM has been discussed extensively on this forum earlier. It is a much tried and tested tool, and extensive field use has established its usefulness. All the same, questions like those raised by Dr Sood should not be perceived as a threat to VVM use; they, hopefully, will help clarify issues and make the case for VVM stronger. And it is better that these perceptions get clarified, especially since they are unscientific. The e-forum is a space for sharing knowledge and field experiences, and this space is generally respected and valued. Errors, if any, are of omission. A list of must-read documents has been included for those who would like to re-familiarize themselves with the issues. ----------- Dr. Sood has once again raised a point which has been discussed time and again in India. The narration is comprehensive and covers different aspects. Has GOI/IAP accepted open vial policy in non-NID settings for OPV? The colour change in VVM to grade III/IV on a OPV vial certainly is a definite indicator for field workers for not using the vial. And also for program managers at all levels to look into the cold chain from manufacturer till it reaches beneficiary. It is true that 4 frozen ice packs is the best indicator for routine immunization but in NIDs/SNIDs where massive resources are required VVM still seems to be a good proxy indicator. S. C. Gupta ([[email protected]][email protected][/email]) Jaipur, India Dear Technet, Your reader comment on the reliability of the VVM is useful if it guides your readers towards the WHO review document, "Thermostability of Vaccines,"which your readers can view at www.who.int. See the discussion on OPV degradation at different ambient temperature levels, starting on page 30. Briefly, the field guidelines for vaccines are much more rigorous than the thermostability of vaccines would warrant. This simply reflects the desire to err on the side of caution. Specifically, OPV can, for hours at a time, stand in ambient temperatures. This explains the use of the fast chain in areas without good peripheral cold chain in remote areas. This is no argument for putting OPV in your shirt pocket when a refrigerator is available. It is a strong argument for not tossing out vaccines when the VVM is at Stage 1 or 2. Bob Davis ([[email protected]][email protected][/email]) American Red Cross Nairobi Dear Moderator I am deeply concerned at the isolated posting of this unscientific, alarming and alarmist anecdote of one group's experience with VVMs. The VVM is a WHO-verified device, which has, within the limitations of batch-to-batch reliability and lot quality assurance, been verified to perform within certain parameters of temperature and light exposure. As you would know, there are four varieties, each of which vary in the rate of colour change according to their photochemical and thermochemical properties, and which in turn determines which type is applied to which kind of vaccine vial (according to the stability of that vaccine). This is clearly outlined in the attached references, and should be understood by all users of VVMs. You might also like to familiarise yourself with the technical information previously provided to me by the manufacturer and from WHO, as referenced below. Sorry I don't have electronic versions of these references. (Has been included in the list below.) I would strongly recommend you to batch the posting of these responses more responsibly, or preferably just refer them to Ms Robertson or Dr Shapiro as originally requested. As Hans Everts pointed out in the earlier posting, it takes a lot to change people's established practices in EPI, and although due care is appropriate in use of VVMs, the isolated experiences of one group (just like those of individual members of the anti-vaccination lobby in relation to immunisation itself) can frighten off a lot of people who would otherwise have used VVMs, as intended and with great benefit to infants and young children around the developing world. David Hipgrave ([[email protected]][email protected][/email]), Chief, Health, Nutrition and WES Section UNICEF China 12 Sanlitun Lu, Beijing China 100600 Dear Moderator, Having spent considerable amount of time managing TechNet21 at WHO HQ (2001-2006), I always believed that we established a working ethic to encourage participation from all levels. However, when it comes to UNSCIENTIFIC contributions, we have to be careful... Encouraging participation should NOT be practiced blindly... It is our responsibility to filter such contributions, otherwise, they will create more CONFUSION and HARM than anything. If one looks back in TechNet21 archives, he/she can find many postings in response to this unscientific contribution. VVM was conceived as a dream in 1979... In May 2007, we have celebrated 10th year of VVM introduction... During its 10-year implementation period, around 2-billion units of VVMs were made to the field, helping health workers to take informed decisions... VVM specifications and verification protocol can be found at the following WHO site: VVM is a prequalified device by the WHO. Validation tests were conducted at independent WHO accredited laboratories. In addition to these tests, all batches are released one-by-one by the manufacturer Temptime Corp., using accelerated tests as well as accepted by vaccine manufacturers through similar tests. There are also a series of random testing of VVMs from the field showing conformity with WHO specifications. Lot release tests are done at 37°C while validation tests are conducted at lower temperatures such as 25°C, 8°C and 5°C. VVM reaction is based on Arrhenius equation which is correlated to vaccine degradation due to heat exposure. In summary, VVM mimics this degradation with a safety margin. The correlation between VVM and the vaccine potency was studied by the WHO and published. This study was first presented at the TechNet Copenhagen meeting in 1998 and was then published by WHO as Testing the correlation between vaccine vial monitor and vaccine potency (WHO/V&B/99.11). The study was designed and evaluated by D J Wood of the National Institute for Biological Standards and Control (NIBSC) in the United Kingdom. The study showed that there was a good correlation between vaccine potency and VVM change for vaccines produced by all four OPV manufacturers supplying vaccine to UN agencies. Since the principle of correlation has been established, WHO did not see any need to further test the potency of each vaccine relative to the VVM response (the relative temperature dependence of VVM reaction (Arrhenius activation energy, remains essentially the same in all four different types of VVMs; however the rate varies with VVM category). In the past, we have seen people dumping the vaccine vials with VVMs in boiling water or in extremely hot ovens claiming that VVMs do not react to these exposures. These unscientific experiments are not pertinent to field conditions. VVMs were tested after submersion in water according to the approved protocol and they conform to the requirement. The manufacturer uses in-process testing of VVMs during production at 60°C and higher. Since we do not keep vaccines in boiling water and/or in hot ovens, I have difficulty in understanding the logic of exposing VVMs to such conditions. Similarly, taking a vial with VVM and exposing it to undefined and uncontrolled temperature will not work to challenge the science behind VVMs (no information was available on the type of VVM, duration of exposure, ambient temperature profile, etc.). If Dr Rajesh K Sood is interested, I strongly suggest him to read the specifications and verification protocols to understand how these tests should be conducted. Since Arrhenius equation is a mathematical calculation, when the temperature exposure over time is known (but the temperature exposure the vaccines most likely to be exposed to - not boiling water or hot oven temperatures), the VVM reaction can be mathematically calculated. This was also tested in a series of laboratory controlled and field studies between 2002-2004, that authors confirmed the perfect match of VVM color change and mathematical calculations (Kartoglu U, Ganivet S, Guichard S, Aiyer V, Bollen P, Maire D and Altay B. Use of cool water packs to prevent freezing during vaccine transportation at the country level, PDA Journal of Pharmaceutical Science and Technology, in press 2008). In summary, the science behind VVM brings together 29 years of experience and many tests at all levels, at the manufacturing facility, independent laboratories, vaccine manufacturers, random testing and field studies. VVM is a validated and prequalified time temperature indicator serving for more than 10 years to health workers to make correct decisions when a vaccine is exposed to a combination of temperature over time. There is absolutely no question about the reliability of VVMs. Dr Sood's contribution has another UNSIENTIFIC statement (or suggestion) - that is to "insist on 4 well-frozen icepacks". This is how you invite "freezing". But this deserves a separate discussion. UMIT KARTOGLU Scientist FCH/IVB/QSS, Room L267 World Health Organization References [list=1] WHO Specifications for VVM: www.who.int/immunization_standards/vaccine_quality/vvm_specifications_e6in5.pdf WHO Technical Session on VVM: www.who.int/immunization_standards/vaccine_quality/08_questions_and_answers_21march02.pdf WHO policy statement (MDVP): www.who.int/vaccines-documents/DocsPDF99/www9924.pdf VVM History and Milestones www.who.int/entity/immunization_standards/vaccine_quality/VVM_history_milestones.pdf Temperature sensitivity of vaccines: http://www.who.int/vaccines-documents/DoxGen/H3DoxList.htm http://www.technet21.org/fichiers_Word/VVM-Interpretation.doc (550K) (POST 01061E: VVM USE) [/ol] Post generated using Mail2Forum (http://www.mail2forum.com)
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