POST00425E: Vaccine wastage due to deadspace in syringes

POST 00425E : VACCINE WASTAGE DUE TO DEADSPACE IN SYRINGES 15 February 2002 ------------------------------------------------------------------ Dr. Birhan Altay, Chief, Control of Biological Products & Logistics Management in the Ministry of Health, Turkey brings a new perspective to vaccine wastage discussions and explains Turkey experience in reducing deadspace in syringes: "I want to share one experience from Turkey on deadspace in syringes with TechNet21 members. The problem was also raised during the New Delhi TechNet21 meeting last summer. The question is whether it is possible to give same amount of doses from a vaccine vial as it is indicated on the label (for example 20 doses out of a 20-dose vial). We often hear that one cannot give more than 17-18 doses from a 20-dose vial and 13-14 doses from a 20-dose BCG vial. The theory is as follows: In the WHO specifications of 0.05 ml autodisable syringe for BCG injections (specification reference E8/DS.2, date 1 January 1998) MAXIMUM deadspace allowed is 25 microlitres. However, this allowable deadspace is also HALF of the dose size! That means each time you have to draw 0.075ml vaccine (0.05ml the dose plus 0.025ml for the deadspace). In theory, with a deadspace of 25 microlitres, you can draw exactly 13 doses in 0.05ml from a 20 dose vial and the 14th dose would be only @ 0.025ml (which actually can only fill the deadspace). As for the 0.5ml AD syringe, WHO allows maximum of 50 microliters deadspace which is only 1/10th of the dose. In this case, from a 20-dose vial you can only give 18 doses in 0.5ml, and the 19th dose would be @ 0.1ml, which is not bad compared to what you get out of a 20-dose BCG vial. Thinking about all wastage discussions, it seems like we are losing 35% of 20-dose BCG vials even under perfect conditions... The problem seems less severe with 0.5ml AD syringe where we speak of 10% wastage due to deadspace in the AD syringe. On the other hand, we know that vaccine manufacturers as part of GMP should kind of overfill the vials to allow same amount of doses to be drawn as indicated in the label, but it is not clear to me whether this is possible to ensure 20 doses from a 20-dose BCG vial. In Turkey, we use locally produced disposable syringes. We are of course aware of the WHO-UNICEF-UNFPA joint statement on the use of auto-disable syringes in immunization services (WHO/V&B/99.25) and working towards switching to AD syringe production. However, since 4 years we have been using specially designed syringes which reduce the deadspace almost to zero. BCG syringe We have extended the needle down through the hub to touch the seal and filled the empty space in hub. By doing this, we do not have any wasted vaccine in the hub, and only wastage comes from the inner space of the needle which is ignorable. 2ml syringe As for the 0.5ml injections, we have modified the design of locally produced 2ml syringe by adding a conic shape protrusion to the seal to fill in the hub. Similarly by doing this, no liquid remains in the hub and only wastage comes from the inner space of the needle, again very minimum." Umit Kartoglu (WHO) explains the overfilling in vaccine vials by giving an example from GSK vaccine DTP-HepB + freeze-dried Hib (based on his communications with P. Tollet, GSK): Two-dose presentation of DTPw-HepB from GSK is overfilled 0.3ml to compensate the following losses during reconstitution and drawing vaccine from the reconstituted Hib vial: loss in DTPw-Hep B vial (remaining liquid) : 0.05 up to 0.1 ml; loss in the needle lumen to reconstitute Hib : +/- 0.05 ml; loss in the vial with the reconstituted Hib (remaining liquid) : +/- 0.05 ml; loss in the needle lumen of the needle for the injection : +/- 0.05 ml; loss during deairing of the syringe before injection : +/- 0.05 ml. Umit says that this underlines the importance of using all of the diluent for reconstitution and not to make a new calculation of how much to take for reconstitution from the diluent. This is also why only the diluents provided with the specific vaccine by the same manufacturer must be used for reconstitution. Vaccines and Biologicals Update (WHO), Volume 34, December 2000, "Proper handling and reconstitution of vaccines avoids programme errors" lists other reasons why the diluents are not interchangeable: "Diluents vary in their composition. Not all diluents are sterile water for injection. This is a common misconception. Diluents may contain: * stabilizers that affect heat lability; * bactericides to maintain the sterility of the reconstituted vaccine; * chemicals to assist in dissolving the vaccine into a liquid; * buffers to ensure the correct pH." ----------------------------------------------------------------------------- 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. 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