Technical Note: Comparison of traditional needle vaccination with pneumatic, needle-free vaccination for sheep.

Lateral transmission of blood-borne diseases can occur when a single needle is used repeatedly to vaccinate livestock. Needle-free technology to vaccinate sheep without damaging the carcass, causing lesions, or leaving needle fragments, and eliciting a similar antibody response as traditional needle vaccinations, has been hampered due to variable wool length. Vaccine delivery, injection time, and antibody response were evaluated for a prototype pneumatically powered, needle-free injector and for traditional needle injections. To determine optimal pressure for vaccine delivery with the pneumatic, needle-free injector, two 8-mo-old wethers were injected at pressures from 207 to 414 kPa in increments of 69 kPa. Injection time and antibody responses were evaluated using one hundred 8-mo-old wethers given primary and secondary inoculations of ovalbumin. Serum samples were collected before and after the inoculations on d 0, 14, 28, and 42. Optimal pressure to deliver a s.c. inoculation with the pneumatic, needle-free injector was 207 to 276 pKa. Inoculation of 100 wethers required 60% less time with the pneumatic, needle-free injector than with needle injections when a new needle was used on every animal. Antibody titers were the same (P > 0.12) for the pneumatic, needle-free and the needle injections on d 14, 28, and 42. In addition, antibody titers increased after primary and secondary inoculations, as expected. This study indicated that a pneumatic, needle-free injector can be used to elicit the same antibody response in sheep as a needle injection, and the pneumatic, needle-free injector was faster. The pneumatic, needle-free injector also would be expected to reduce lateral transmission of blood-borne diseases, and will save time, eliminate biohazard waste (e.g., used needles), and eliminate accidental needle sticks for livestock handlers when vaccinating sheep.