POST 01059E : DILUENTS

POST 01059E : DILUENTS Follow-up on Post 01054E 27 February 2007 _______________________________ This posting contains three contributions. The first is from Femi Odebgami (mailto:[email protected]) from Nigeria. The second is from Karan Singh Sagar (mailto:[email protected]) from India and finally, the third is from Diana Chang Blanc (mailto:[email protected]) from WHO in Geneva. Diana had sent the very same WHO document to which Femi refers. It is NOT attached to this posting but can be downladed directly from : http://www.who.int/vaccines-documents/DoxNews/updates/updat34e.pdf A similar discussion took place on TechNet in August-September 2002 (Posts 00491E, 00494E and 00501E) Then Ãœmit Kartoglu had also sent the same document. I make a short comment after Femi's contribution. _______________________________ Dear moderator, Reading to Dr Kiran's questions I said to myself this is how the problems start. Being involved in investigating some adverse event following immunization (AEFI) clusters and reading reports from others, with great certainty I can say that using another kind of diluent is one of the main causes for AEFI. If it was that simple vaccine manufacturers would simply provide sterile water. Every ampoule or vial of diluent is specifically produced for a particular vaccine, and this is indicated on the diluent label. Every health worker involved in immunization should follow the golden rule: Always use the diluent that comes with the vaccine. WHO Vaccines and Biologicals Update Volume 34, December 2000 is a perfecct document on proper diluent use. The document clearly indicates that diluents are not simply sterile water and they may consist of the following: • stabilizers that affect heat lability; • bactericides to maintain the sterility of the recocnstituted vaccine; • chemicals to assist in dissolving the vaccine into a liquid; • buffers to ensure the correct pH. Although this document is seven years old, I believe it is still very valid. However, there is one thing that I am not too much convinced - thermal shock. I could not find any reference on this. All other documents referring to thermal shock use this Update as a reference. Does anybody know where this evidence is coming from? Coming back to diluent use issue, I would like to quote an information from an old WHO web site - which does not exist any more. I found this as a printout among my files and wanted to share with TechNet21 subscribers: Ten critical steps to reconstitute vaccines safely: 1. Read the label on the diluent to be sure that it is the correct diluent provided by the manufacturer for that specific vaccine and vial size. 2. Check the expiry date to make sure that it has not passed. 3. Check the status of the VVM to make sure that it is not at or beyond the discard point. Discard the VVM during reconstitution. 4. Cool the diluent to below +8 C, preferably a day prior to its use. 5. Draw the entire content of the diluent into a new sterile mixing syringe and empty the entire contents of the diluent into the vaccine vial. 6. Discard the used mixing syringe and needle into a safety box without recapping. 7. Do not leave the mixing needle in the vaccine vial. 8. After reconstitution, wrap the vaccine vial in dark paper or foil or insert in a foam pad of a vaccine carrier. Never allow the vial to become wet or immersed in water. 9. Discard all reconstituted vaccine at the end of the session, or within 6 hours, whichever comes first. 10. Use a new sterile syringe and needle to withdraw each dose of the vaccine and use the same needle and syringe for injecting the vaccine. After giving the injection, drop the used syringe and needle into the safety box without recapping. Hope you find this useful. Regards, Femi ------------------------- COMMENT : As Femi, I have had similar doubts about this notion of "thermal shock". I will not repeat any detail here, but four and a half years ago, at the end of Post 00501E, I had made a substantial comment and asked questions for which I unfortunately never received any answer. For those interested, you can download this archived posting directly from : http://listes.ulaval.ca/cgi-bin/wa?A2=ind0209&L=technet21e&T=0&X=0C6E9163017F13C27E&Y=technet21%40ccisd.org&P=695 The moderator ------------------------- The BCG & Measles vaccine need to be reconstituted only with the diluents supplied by the same manufacturer in order to maintain the required chemical, physical composition, Ph etc. Using a different diluent or a diluents from another manufacturer will damage the vaccine and make it ineffective and also can lead to serious AEFI. In case a different manufacturer's diluents is used and a serious AEFI occurs then the manufacturer can plead that the vaccine was not reconstituted properly as per instructions provided in the product insert and no action can be initiated by the NRA's even though there may be vaccine related AEFI. Thanks and Best Regards Dr Karan Singh Sagar ----------------------------- Lyopholized (freeze-dried) vaccines are produced, approved for marketing and 'packaged' with diluents that are specifically designed for the needs of that vaccine. They are never interchangeable and although may appear to be simple water, in fact typically contain a variety of chemicals and additives. These may include : • stabilizers to improve heat stability of the vaccine; • bactericides to maintain sterility after reconstitution; • chemicals to assist in dissolving the vaccine into a liquid; • buffers to ensure the correct acidic balance of the mixture. Additionally, diluents vary in their volume such that reconstitution of vaccines with diluents which are not their intended 'partners' may result in failure to draw up the correct number of doses per vial; otherwise said, may result in over or under-concentration of the antigenic content of the vaccine dose. Therefore, using a diluent that is not specifically manufactured for that vaccine, including replacing diluent with sterile water, may result in altered vaccine efficacy and provoke adverse events which can range from mild to very severe. Attached please find a document that further outlines proper reconstitution techniques. Diana Chang Blanc Technical Officer, EPI WHO/HQ ______________________________________________________________________________ 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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