Friday, 27 September 2002
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POST 00505E : USE OF VVMs TECHNET21 E-FORUM Technical network for strengthening immunization services Contributions to: mailto:[log in to unmask] or use your reply button! -------------------------------------- POST 00505E : USE OF VVMs 27 September 2002 ________________________________________________________ Ümit Kartoglu (mailto:[log in to unmask]) from WHO reacts to previous comments on the use of VVMs. ________________________________________________________ In POST 00480E (29 July 2002) Carib Nelson (PATH) suggested that "since it (OPV) is the least stable vaccine, it would seem reasonable to assume that in an outreach box with a mix of vaccines, if the OPV VVM is still OK then the others vaccines should be OK as well." In POST 00482E (31 July 2002), Robert Steinglass (BASICS) underlined that "the most heat-sensitive vaccine is not OPV, but reconstituted measles." In the same posting, Anthony Battersby suggested a correction to Carib's thinking that "you can only use OPV as a proxy if all the other vaccines have followed the same cold chain up to the moment that you wish to use OPV as a proxy." It is thus necessary to stress the following two points : 1. If vaccines were listed in order of heat sensitivity, OPV would be at the top of the list followed by measles. This list is based on vaccine stability tests at 3°C. Whatever their rank in the list however, all freeze-dried vaccines must be discarded 6 hours after reconstitution or at the end of the session whichever comes first. For example, BCG is more heat stable compared to DTP, but it (BCG) has to be discarded 6 hours after its reconstitution while DTP can still be used in subsequent immunization sessions in accordance with the multi-dose vial policy. This is also why VVM on a freeze-dried vaccine is always placed either on top of the cap of a vial or on the neck of an ampoule.Then it is discarded during the reconstitution process and cannot be referred to anymore. As for liquid vaccines (like DTP), VVM is always placed on the label, visible at all times even after the vial is opened. 2. WHO never recommended the use of one type of VVM as a proxy indicator for vaccines without VVM. WHO states that "vials with VVMs should NOT be used as proxy indicators of heat exposure for vials without VVMs. Vials without VVMs should be handled as they always were." This also applies to the same type of vaccines that VVM on a vial of OPV cannot be used as proxy indicator for OPV vials without VVM. What Anthony describes as a condition for using OPV VVM as a proxy indicator should also be disregarded. ----------------------------------------------------------------------------- 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. As soon as administratively possible, TechNet21 e-Forum will operate 3 language-specific lists in English, French and Spanish. The comments made in this forum are the sole responsibility of the writers and do not in any way mean that they are endorsed by any of the organizations and agencies to which the authors may belong. ----------------------------------------------------------------------------- CONTRIBUTIONS: Contributions to: or use your reply button! The TechNet21 e-Forum welcomes new subscribers who are involved in immunization services. 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