Splash-back has been previously reported upon in scientific studies. A 1966 article titled, Vaccination by Jet Injection, published in the British Medical Journal stated, “There is no risk of cross-infection unless the face of the injector is contaminated with blood or tissue juices” (Anonymous, 1966). Although studies have demonstrated the nozzle of the jet injector indeed becomes contaminated during jet injection.
- Hoffman and colleagues (2001) observed the nozzle and internal fluid pathway became contaminated during the jet injection process amongst several brands of jet injectors, including the Ped-O-Jet and Med-E-Jet. He termed this phenomena as ballistic contamination, whereupon the force of impact caused a release of pressure which expelled debris away from the site of impact (Voelker, 1999). With the jet injector being directly behind the site of impact it is a prime target to becoming contaminated.
- Lipson and colleagues (1958) assessed if the antibody response to a poliomyelitis vaccine via jet injection would be comparable to needle and syringe. In the study, thirty-four children received two doses of polio vaccine via a handheld Press-O-Jet injector and twenty-seven children received one dose of vaccine by needle. Lipson stated, “We observed blood on the nozzle of the jet injector on two different occasions.” This means in 3 percent of the injections blood was observed on the jet injector nozzle, indicating the nozzle became contaminated due to splash-back.
- Kutscher and colleagues (1962) warned of splash-back within their paper. “The Hypospray unit itself is not sterilized although the head can and should be disinfected,” stated the researchers. If the patient’s arm is not properly held “some portion of the injected material may rebound and not attain its target” (emphasis added). In other words the injected material would splash back onto the jet injector.
- Dr. Sol Roy Rosenthal studied the transference of blood via the Hypospray Multidose jet injector amongst children at two schools. Observations from the first school found the jet injector produced “much bleeding.” Overall the study found in 17 percent of the vaccinations of school children there was enough blood on the jet injector nozzle to transmit blood-borne pathogens (Rosenthal, 1967).
- Horn, Opiz and Schau (1975) observed splash-back through their investigations of the Hypospray Multidose and warned of the risk this posed in spreading hepatitis. Horn stated,
We were able to demonstrate by direct staining of material obtained from the nozzle, that this part of the injector becomes contaminated with material originating in human white blood corpuscles. These findings are very similar to those of Hughes with syringes and have an obvious implication in relation to the transfer of hepatitis virus by jet injectors (Horn, Opiz & Schau, 1975).
- By 1973, a scientific article had acknowledged the concern raised by previous researchers. The researcher, H.D. Wilson from a county health department in Scotland, even acknowledged that “during high-pressure injection, traces of blood may cover the inside of the bell [of the jet gun nozzle] adjacent to the skin, and the possibility of transfer of…hepatitis must be considered…” (Wilson, 1973).
- Han and colleagues (2011) tried to overcome the threat of back splash with a needle-free micro jet injector. The researchers found,
A conventional drug jet may possess a volume in the range of 30 to 100 microliters, while the proposed microjet maintains a volume of a few hundreds of microliter, preventing back splash of interstitial liquid and delivering the same amount of drug by concentration change or multiple injections. This back splash is mainly caused by a large injected jet volume and is responsible for cross- contamination. (emphasis added) (Han et al., 2011)
To put this into perspective, the Ped-O-Jet manual lists the device can administer dosages between 0.1 cc to 1.0 cc, or rather 100 to 1000 microliters (Ped-O-Jet International, 1991). The average dosage for an immunization administered by a Ped- O-Jet within the DoD was 0.5 ml, or rather 500 microliters (DoD, 1970). As Han has reported, back splash was greater with larger injected volumes. The average dosage administered by a Ped-O-Jet was 500 times greater than dosages administered with the micro jet injector. The degree of backsplash would be greater allowing for cross- contamination.
- Cu and colleagues (2020) observed splash back with a needle-free micro jet injection. The researchers used micro cinematography to capture a simulated jet injection. Within their paper, in figure 6a, bottom photo, “[T]he yellow circles show the back-splashes of the jet. The distance between the microfluidic device and the skin sample is 7.3 mm…” (Cu et al., 2020)
- Portaro believed “enhancing the current knowledge of the fluid dynamics relating to jets penetrating human skin can help alleviate the problems associated with backsplash which leads to cross contamination among patients” (Portaro, 2013).
- Yoh and colleagues (2016) noted the risk of cross-contamination from splash-back. The researchers also noted the specific parameters which need to be met to avoid splash-back.
Contrary to expectations, liquid jet injectors have the potential for cross- contamination from splash-back during injection if not high enough speed and not narrow enough jets are used, resulting in poor reliability of delivery dose and depth, and insignificant or no reduction in pain. (Yoh et al., 2016)
This research serves as evidence that the nozzle face of the jet injector becomes contaminated during the injection process.
- (Anonymous, 1966) Anonymous. Vaccination by Jet. Br Med J December 31, 1966: 1610.
- (Cu et al., 2020) Cu K., Bansal R., Mitragotri S., Rivas DF. Delivery Strategies for Skin: Comparison of Nanoliter Jets, Needles and Topical Solutions. Annals of Biomedical Engineering, 48 (7); July (2020). pp. 2028-2039.
- (DoD, 1970) Department of Defense. Immunization. TB MED 114; NAVMED P-5052-15A; AFB 161-9. By Order of the Secretaries of the Army, the Navy, and the Air Force. 25 May 1970. 33 pages
- (Han et al., 2011) Han T., Han J., Yoh JJ. Drug injection into fat tissue with a laser based microjet injector. Journal of Applied Physics, 109, 093105 (2011).
- (Hoffman et al., 2001) Hoffman PN, Abuknesha RA, Andrews NJ, Samuel D, Lloyd JS. A model to assess the infection potential of jet injectors used in mass immunization. Vaccine 19 (2001): 4020-4027.
- (Horn, Opiz & Schau, 1975) Horn H, Opiz B, Schau G. Investigations into the risk of infection by the use of jet injectors. Health and Social Serv J 85:2396–2397, 1975.
- (Kutscher et al., 1962) Kutscher AH, Hyman GA, Zegarelli EV, Dekis J, Piro JD. A comparative evaluation of the jet injection technique (Hypospray) and the hypodermic needle for the parenteral administration of drugs: a controlled study. Am J Med Sci 1962;54:418-420.
- (Lipson et al., 1958) Lipson MJ, Carver DH, Eleff MG, Hingson RA, Robbins FC. Antibody response to poliomyelitis vaccine administered by jet injection. Am J Public Health 1958;48(5):599-603.
- (Ped-O-Jet International, 1991) Ped-O-Jet International. Instructions for the operation and maintenance of the Hypodermic Jet Injection Apparatus, Ped-O-Jet (foot operated) [Model POJ, NSN 6515-00-910-0097, rev. date 070191]. Cherry Hill, NJ 08002, USA.
- (Portaro, 2013) Portaro R. Air-Powered Liquid Needle Free Injectors: Design, Modeling and Experimental Validation (thesis). Concordia University. February 2013.
- (Rosenthal, 1967) Rosenthal SR. Transference of blood by various inoculation devices. Am Rev Respir Dis. October 1967; 96(4):815-819.
- (Voelker, 1999) Voelker R. Eradication Efforts Need Needle-Free Delivery. JAMA May 26, 1999;281(20):1879-1881.
- (Wilson, 1973) Wilson HD. Experience of BCG Vaccination by Jet Injection in an Outbreak of Primary Tuberculosis. Lancet April, 28 1973; 1(7809):927-8.
- (Yoh et al., 2016) Yoh JJ., Jang H., Park M., Han T., Hah J. A bio-ballistic micro-jet for !drug injection into animal skin using a Nd:YAG laser. Shock Waves 26, 39-43 (2016).