POST 00501E : CHILLED WATER PACKS STUDY

POST 00501E : CHILLED WATER PACKS STUDY Follow-up on Posts 00485E 15 September 2002 ________________________________________________________ Sam Kamau (mailto:[log in to unmask]) from Kenya expresses some concerns about chilled waterpacks followed by comments by Michel Zaffran (mailto:[log in to unmask]) from WHO about keeping vaccines in holes of foam pads. I have put both these comments under "Chilled Water Packs" although Michel's contribution isn't directly related. The "More Cold-Sensitive Vaccines" issue was really about protecting some vaccines from freezing that is not normally the issue for reconstituted measles. _______________________________________________________ I am rather concerned to read this article concerning the use of cool or wet icepack during the measles administration after the reconstitution . The health workers know that reconstituted measles and BCG should always be kept on a frozen icepack for the six hours. The the issue of monitoring the six hours duration is also very critical. The issue of using cool or wet icepack will definitely waterdown the importance of the health workers sensitivity to the use of the frozen icepacks in the overall vaccine management and should not be discussed in any forum. Sam Kamau National EPI Logistician Kenya ___________________________________________________________ The use of the foam pad and putting vials of vaccines in the holes of the foam pad was an approach promoted 10 years ago to avoid that icepacks be removed from the vaccine carrier thus substantially reducing its cold life and all potentially jeopardizing the other vials inside the carrier If ice or additional icepacks are available then they should be used to keep the open vials cold (these would be in addition to those needed to keep the vaccine carrier cold : i.e. the full load of icepacks recommended by the manufacturer for the expected cold life of the carrier). However if one has to choose between keeping the vial in the foam pad or removing one of the icepacks from the carrier and putting it on the table to keep the open vial cold, then I believe the foam pad is a better choice Michel ______________________________________________________________ Moderator's comments : It is true that policy changes may generate some confusion. However at this point I wish to stress that no such change has occurred. It should also be clear that if and when chilled waterpacks are approved by a revised WHO policy document this would apply only for vaccine transportation. Reconstituted vaccines such as measles for example, have to be kept within a temperature range of 2° to 8°C for a maximum of 6 hours. I also wish to use this opportunity to put my own questions forward to the Technet audience. I wonder if other members have had similar thoughts. And this is about the diluent. I have shared the accepted truths so far. However I have been puzzled lately to the point of doubting these truths. And I wish to have your comments and hopefully some answers that I haven't found to my satisfaction yet. Even before publishing the posting in which the temperature of the diluent was discussed (Post 00494E), I had questions when consulting the manufacturer's notice of measles in North America (marketed as MMR but each component is produced separately). It is recommended that the diluent be kept at room temperature to save cooling space in the refrigerators and it doesn't require that it be cooled before reconstitution. I further discussed with a scientist working at the manufacturer. They maintain that a warm diluent even at 43°C cannot harm the virus, the so-called "thermal shock" to the vaccine is not known and the diluent should be kept and used at ambient temperature as per their recommendation. But incubation does harm the virus and reconstituted measles vaccine has to be kept cool at 2°-8°C. This tends to confirm the principles of virus biology and what happens to a live virus in a vaccine solution, although I admit these principles I acquired a while ago. There are few absolutes in science and as we all know scientific truths change sometimes. I got also puzzled by the interpretation we probably all made of the part of the article posted in POST 00494E. If the diluent was prewarmed at 41°C and then incubated at that same temperature, how can we scientifically draw the conclusion that the warm diluent harmed the virus as compared to the incubation? In the meantime I came upon another article that had been published on the same topic before the one referred to in the posting (Peetermans J, Colinet G, Stephenne J, Bouillet A., "Stability of freeze-dried and reconstituted measles vaccines", Dev. Biol. Stand. 1978;41:259-64). It had concluded differently that "Reconstitution with diluent at 41° C and subsequent exposure to this temperature does not affect the titer significantly during the first half hour." So where is the truth? Is it that titers were measured with different methods? Can this differ depending on the manufacturer? So I leave it to you all to bring some further light on this point. I admit to my own confusion. Claude Letarte _____________________________________________________ CONTRIBUTIONS: Contributions to: or use your reply button! The TechNet21 e-Forum welcomes new subscribers who are involved in immunization services. SUBCRIBE: To subscribe, send an e-mail to: Leave the SUBJECT area BLANK, do not type anything. In the body text, just write: Subscribe TECHNET21E Surname Name Do not use any accents in your name and surname. UNSUBSCRIBE: To unsubscribe, send an e-mail to: Leave the SUBJECT area BLANK, do not type anything. 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