BACKGROUND & AIMS
Intradermal vaccination is often preferred over intramuscular vaccination due to its dose-sparing capability, hereby increasing the efficiency (less volume needed for the same immunologic reaction) and decreasing the cost of a vaccine. Another factor that raises the cost of a vaccine, is the overfill or waste product per injection. Overfill cannot be avoided because fluid stays behind in the syringe tip and needle cavity. Therefore, the aim of this study is comparing the wasted volume and dose accuracy of dose sparing vs non dose sparing syringes in combination with different intradermal adaptor pieces including the VAX-ID device.
MATERIALS & METHODS
The amount of overfill is measured for regular 1ml syringe vs dose-sparing 1ml syringes and for 32G needles vs Multipins vs VAX-ID. In total, 9 tests were performed of which 7 with a 32G needle and 2 with Turtlepin III (7 pins of 2.0 mm and 19 pins of 1.0 mm). For each test, a new syringe and needle was used. First, 0.20cc fluid (saline solution; 0.9% NaCl) is drawn from a vial. As a next step, fluid is ejected directly on the tray of mass balance until the plunger cannot be pushed further. The weight of the ejected fluid can subsequently be read with an accuracy of 0.1mg and converted to a volume scale. By subtracting the volume of ejected fluid from the amount of volume withdrawn from the vial, the amount of overfill can be determined.
Tests with a regular syringe in combination with a 32G needle have shown that an overfill of 0.03ml is required when injecting 0.19cc. The total volume that needs to be withdrawn from a vial totals 0.22cc with waste volume representing 14% of the total volume. Using a dose sparing syringe combined with a 32G needle results in a decrease in overfill to 0.01cc on an injectable volume of 0.19cc. The percentage of waste volume to the total volume of 20cc equals 5%. The dose sparing syringe combined with a Turtlepin III with 7 pins raises the needed overfill to 0.15cc, indicating a waste percentage of 75%. The dose sparing syringe combined with a Turtlepin III with 19 pins further increases the overfill to 0.19cc or 95% of the total volume.
VAX-ID proofs to have dose-sparing properties requiring an overfill of merely 5%. This is 9% less overfill compared to other intradermal injections techniques/devices using a regular 1ml syringe and 75-95% when using the Turtlepin III.