Thursday, 07 August 2003
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POST 00590E : SHAKE TEST Follow-up on POSTS 00571E, 00574E, 00575E and 00579E 7 August 2003 _________________________________________________ We post here some further exchanges between members concerning the Shake Test. Pham Ngoc Len (mailto:[log in to unmask]) had a practical question for conducting the test and Ümit Kartoglu (mailto:[log in to unmask]) is commenting. It is good news that Ümit announces a study on the shake test. I believe that it will help clarify a number of issues and may bring a better standardization of the test. _________________________________________________ Thank you very much for your response to my concerns. I have the following issue that I would like to have clarified. In the guidelines for the shake test that I have a copy it says that: "Prepare a frozen control sample: Take a vial of vaccine of the same type and batch number as the vaccine you want to test, and made by the same manufacturer. Freeze the vial until the contents are solid, and then let it thaw. This vial is the control sample.'' The question here is how long and at what temperature the control sample has to be frozen. Do I freeze it at 20°C below zero for 20 hours? Do I freeze it at 10°C below zero for 12 hours? Or do I freeze it at 5° C below zero for 12 hours? Which one is correct? Any scientific support for freezing a control sample? I am afraid that a copy of the guidelines I have is an incomplete one so it is really difficult for us. Thank you very much in advance for your explanation. Len ___________________________________ For how long we should freeze the control vial ? It is not possible to give a universal recommendation regarding the required time for freezing of a vial. This depends on various factors such as the type of vaccine, manufacturer, vial size, refrigerator type, and freezer temperature. The shake test protocol asks for the control vial to be "solid" frozen. I believe this is a clear description of what is needed to have a control vial in hand. This may take several hours or say a day. One may argue what happens if one thinks that it is solid frozen but right in the middle section of the ice there is a small liquid not frozen yet. We know what happens when the vaccine is frozen: the lattice is broken and this disassociates the antigen from the adsorbent. Therefore, if a control vial is not fully frozen and a fully frozen test vial is compared against it, the test vial sedimentation rate will be faster than the control vial. This result is interpreted as FAILURE and vaccine must not be used and discarded. Of course, a non-frozen control vial is not a proper control vial. To be on the safe side, it is highly recommended to wait for extended hours to make sure that the vial is completely frozen, without following a time limit. When to discard the vial based on shake test result? It is always advised to consider the results of a shake test as FAILURE if one is not sure about the sedimentation rate difference of control and test vials. However, if you are confident that the test vial is behaving slower compared to control vial, the vaccine can safely be used. If a solid ice state is seen in a vial, there is no need to contact any test, this vial must not be used and must be discarded. We are in the process of collecting all samples of freeze-sensitive vaccines to conduct shake test for various scenarios and will share the results with TechNet21 members. I have conducted personally so many shake tests that do not remember the number. I have found it always very fascinating and so clear that it works perfectly. I do not recall any case I experienced that I was not sure how to interpret the result. I am not sure regarding the possibility of adding a chemical to the vaccine which would change color when frozen. I will leave this to vaccine industry and vaccine production/quality experts. Ümit ________________________________ 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. It is moderated by Claude Letarte and is hosted in cooperation with the Centre de coopération internationale en santé et développement, Québec, Canada (http://www.ccisd.org) ______________________________________________________________________________
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