The injection of large numbers of people during a mass vaccination is difficult and expensive without an automated device. However, it is essential that the device is safe and does not harm patients.


In the past the military and public health officials used a jet injector with a hypodermic needle to vaccinate recruits and people during epidemics.


Disadvantages of the needle jet injector:

(1) trauma at the injection site, with bruising and pain

(2) possible transmission of viral infections


Needle-free injectors use a high-pressured jet of inert gas to drive the vaccine into the dermis and subcutaneous tissue of the patient.


However, viral hepatitis B has reportedly been transmitted by these devices. This is due to retrograde contamination of the nozzle head by body fluids released from a patient by the pressure wave. Viral hepatitis B is highly contagious and can be transmitted by minute amounts of blood. In theory other pathogens could be transmitted but this would be less likely.


Risk factors for disease transmission with a needle-free jet injector:

(1) failure to comply with administration instructions

(2) failure to clean the device properly

(3) failure to use an injection nozzle that minimizes retrograde contamination with body fluids


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