Friday, 25 November 2005
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POST 00860E : COMBINATION VACCINES, LYOPHILIZED VACCINES, DILUENTS AND VVMS Follow-up on Posts 00847E, 00852E, 00855E and 00858E 25 November 2005 _____________________________________ This posting contains four contributions to the discussion. The first is from Bruce Weniger (mailto:[email protected]) from CDC in the USA. The second is from Anil Varshney (mailto:[email protected]) from India. The third originally in French, is from Serge Ganivet (mailto:[email protected]) from WHO in Zimbabwe, and the last from Mogens Munck (mailto:[email protected]) from Spain. _____________________________________ I found thoughtful and useful Michel Zaffran's summary of the dilemma in coming up with a practical, understandable policy regarding where to put the VVMs and what guidelines WHO might propose about lyophilized-liquid combination vaccines that require end-users to reconstitute a powdered vaccine with a separate liquid vaccine acting both as diluent and antigen. Although these "field-mixed combos" have been in use for at least a decade in developed countries, it seems likely some confusion and increased medical errors will occur in some developing country settings at the grass roots. It's going to be helpful, but likely expensive, to conduct the antimicrobial inhibition studies to be sure that the preservative will work over the recommended period of storing multi-dose vials for any liquid-lyophilized combinations such as DTPw-HIB and DTPw-HBV-HIB. Maybe it's already been done by their manufacturer(s). Has anyone asked? The last time I checked WHO policy, multi-dose vials stored in the refrigerator between withdrawals could be kept until empty or until expiration, whichever occured first, without any ticking clock (e.g., 1 week, 1 month, etc.) once opened. (Note : I believe that the policy says it could be kept 4 weeks if all conditions are met; the moderator) See: World Health Organization. WHO Policy Statement: the use of opened multi-dose vials of vaccine in subsequent immunization sessions. Geneva: Department of Vaccines and Biologicals, WHO, 2000 (document WHO/V&B/00.09); http://www.who.int/vaccinesdocuments/DocsPDF99/www9924.pdf Bruce G. Weniger, MD, MPH Assistant Chief for Vaccine Development Immunization Safety Office Centers for Disease Control and Prevention Atlanta, GA USA ---------------------------------- Dear Michel, While your suggestion would be technically feasible but looking at the field experience and the practical aspect, my suggestion is that the lypholised and liquid vaccines should not be mixed because it will create more confusion. Every step and activity in the field specially in remote areas should be as simple and straightforward as possible to avoid mistakes and lapses. It may be better to introduce pentavalent vaccines as single vaccine rather mixing them. With kind regards, Dr Anil Varshney New Delhi India ---------------------------------- Michel, In addition to all the questions you raised, there is also the issue of the quality of the VVM on the DPT-HepB vial, which serves as diluent for Hib. This question of keeping the reconstituted DPT-HepB-Hib according to the MDVP policy already implemented in countries, was discussed several times in Zambia and Malawi. In the final analysis, the answer has always been NO because of too high risks of confusion. -Is it a Hib reconstituted with a diluent X? Not easy to verify. -Is it a DPT-HepB-Hib, but what was the state of the VVM on the DPT-HepB vial ? There are no reliable means to verify this, more so if the DPT-HepB could have frozen. No "shake test" is carried out because there is no obvious doubt. The problem remains even if the vial was not stored, but to a lower extent because it is discarded at the end of the immunization session. -Some countries use DPT as a booster and therefore could as well use it instead of DPT-HepB to reconstitute Hib vaccines. Personally, I think the risk of confusion with other lyophilised vaccines is too high. Health workers can be made aware of reducing wastage, without taking such risks. Serge -------------------------------- Hi Michel, I do not feel qualified to comment on the risk, but if, and I say IF, it were possible to reconstitute for example the measles vaccine with another antigen containing a preservant, it would not be necessary to have ice packs available at the session site for keeping the vaccine cool after reconstitution. The amount of ice packs required, particularly in measles campaigns for the age group 9 months to 15 years, and the "freezing power" required for freezing them, are enormous, typically 2-3 times the amount of ice packs used for a polio NID. A big logistical problem would therefore be solved. Regards to everybody, Mogens Munck ______________________________________________________________________________ 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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