Vaccination with an innovative pressure-adjustable needle-free injection device

The Valery® is an innovative pressure-adjustable needle-free injection device (NFID). The objective of this study was to determine appropriate operation of this NFID for vaccination by evaluating the location of a vaccine in pigs after application. In a first trial, 4 groups of 12 pigs weighing respectively 4-5 kg, 6-7 kg, 8-10 kg and 15-20 kg were injected with a dye-labeled vaccine (Circovac, Merial), 0.5 mL in the neck using the NFID. Per group 3 pressure settings of the device were tested (A:low, B:medium or C:high), 4 pigs each. The pigs were immediately euthanized and frozen in vertical position (48 h; -20°C). Cross-sectional slices (3 per pig, 1 cm thick) at the injection sites were collected and digitalized by photography. The slices were checked on the penetration and dispersion of the vaccine by image analysis. In a second trial, 2 groups of 4 pigs weighing respectively 6-7 kg or 8-10 kg were used. Following cleaning and drying of the skin surface, the vaccine was injected using the NFID, in the neck. Before injection a piece of blotting paper in an empty screw cap tube had been weighed. Just after injection, the piece of paper was applied on the skin surface at the injection site for 2 secs , then stored in the screw cap container. The tube was weighed. The percentage of vaccine dose on the skin surface (SkQ) was calculated by difference. The depth of penetration of the vaccine whatever the weight group or pressure settings was 2.33±0.76 cm (n=48) with no difference observed between the pressure settings (A, n. 16, 2.14±0.77; B n. 16, 2.61±0.72; C, n. 16, 2.23±0.75 cm) or the weight group (4-5Kg, n.12, 2.18±0.4; 6-7Kg, n. 12, 2.40±0.24; 8-10Kg, n. 12, 1.89±0.56; 15-20Kg, n. 12, 2.83±1.18 cm) . The percentage of the vaccine present at the muscular level was varying between 70% (pressure A, 4-5kg) to 100% (pressure C, 6-7 Kg). In the different weight groups on average 87.0%. Setting B and C had the highest amount IM, resp.92.5 and 89.2%. The area of muscular distribution is the highest with pressure C compared to A and B (p=0.04). In trial 2,the SkQ was low whatever the operating pressure (A: 3.5±2.2%; B: 2.9±1.9%; C:1.5±0.4%) and the weight groups with a significant inverse relation between operating pressure and SkQ as well as a remarkable uniformity at the highest pressure setting. Under the conditions of the study, the Valery NFID was shown to deliver a 0.5 mL vaccine recommended for IM vaccination satisfactorily. It is advised to use pressure settings medium to high. The volume of vaccine spread on the skin was considered as acceptable. Vaccination compliance was thought not to be impacted by the NFID.