Revisiting Ismach’s 1959 Patent Reveals Ped-O-Jet was Unsterile

Aaron Ismach’s invention of the Automatic Jet Hypodermic Injection Apparatus, more commonly known as the Ped-O-Jet, attempted to overcome the risk of transferring hepatitis during mass immunizations. Although a review of his 1959 patent demonstrates the risk was not eliminated.

Patents contain an abundance of information. Amidst the detailed description about the uniqueness of the invention, a patent describes specific problems the invention intends to resolve.

Ismach proclaimed, “One of the outstanding benefits conferred by the invention in helping to prevent hepatitis or other cross-infection, is that if operation of the jet injection device is commenced in a sterile condition, the gun will maintain its own sterility” (Ismach, 1962).

Although this would also mean if the device failed to “maintain its own sterility” then it failed “to prevent hepatitis or other cross-infection.” This point is further upheld by Ismach stating, “the danger of cross-infection is almost completely avoided” (emphasis added) (Ismach, 1962). Ismach never declared the risk of cross-infection was completely avoided. He could not proclaim his own device was risk-free so he minimized the danger, as evidenced within this patent.

As the patent shows, Ismach believed the risk of transferring hepatitis was contingent upon whether the device became unsterile during the vaccination event.

Did the jet injector ever become unsterile? From Ismach’s patent, we can ascertain that yes, jet injectors, including his Ped-O-Jet device, were frequently unsterile.

Ismach claimed that his invention is “free from danger of sucking fluid back from a patient either during or after the firing cycle is completed so that the danger of cross-infection is almost completely avoided” (emphasis added) (Ismach, 1962).

Here Ismach subtly discloses that after the jet injector was fired there was fluid—whether splash-back of vaccine, blood, or tissue cells—upon the nozzle orifice. Any fluid upon the nozzle following an injection should have been recognized as contamination and thus the device was unsterile.
“Sucking fluid back…after the firing cycle” = Fluid Suck-Back
Ismach proclaimed that his invention was free from sucking fluid back after the firing cycle. He declared that failure to prevent fluid suck-back allows for “cross-infection” and states cross-infection is dangerous. Here Ismach was describing the undesirable phenomenon, so appropriately termed as fluid suck-back.

However, subsequent research has revealed the Ped-O-Jet was no exception to fluid suck-back.

  • The Department of Defense recognized the Ped-O-Jet was capable of sucking fluid back within a 1967 military specification. The specification alluded that conducting a performance test upon every Ped-O-Jet would remove any defective devices. “On cocking the gun, there shall be no drawback of fluid at the jet nozzle,” stated the specification (DoD, 1967; DoD, 1975). However, the performance test conducted was inadequate as it only evaluated fluid suck-back based upon a limited set of parameters and did not represent real life use of the device.
  • In 1977 researchers within the CDC’s Hepatitis Laboratories Division in Phoenix, Arizona, independently—and secretively—assessed the safety of Ped-O-Jet injectors. In their observations, a drop of fluid was observed on the nozzle orifice after firing an injection. “The drop would disappear (back into the injection nozzle head) in 3 to 5 seconds if the gun was held vertically or the drop would disappear immediately if the gun was cocked in a horizontal position” (CDC, 1977). These investigations represented real-life use of the Ped-O-Jet.

The CDC concluded that “disappearance of the fluid drop are common during clinical use of the jet injector” (CDC, 1977). Therefore fluid suck-back was not evidence of a defective device but of an inherent problem with the Ped-O-Jet in general.
“Sucking fluid back…during firing cycle” = Retrograde Flow
Ismach proclaimed that his invention was free of sucking flood back during the firing cycle. Ismach stated, there was “no danger of cross-infection, since nothing but the inoculating fluid itself penetrates beneath the skin of the patient” (Ismach, 1962). Yet the phenomenon of retrograde flow disproves this claim.

  • In October of 1998, the World Health Organization conducted a simulated field trial to assess the degree of blood transmission via Ped-O-Jet injectors. Swabbing the nozzle of the Ped-O-Jet did not eliminate but only slightly reduced the degree of contamination. This finding indicates contamination was present inside the injector’s internal fluid pathway, beyond the reach of swabbing the nozzle, due to retrograde flow (Hoffman et al., unpublished).
  • Hoffman also found retrograde flow within his laboratory investigations of four different jet injectors. A Ped-O-Jet device, renamed as the Am-O-Jet, was apart of this investigation. Hoffman found retrograde flow was a natural phenomenon within the jet injection process. Hoffman stated,

Injectors that have direct skin contact will form a continuous fluid pathway between the skin and injector. As the outward pressure from the injector dies away at the end of an injection, back-pressure from the fluid in the tissue pocket will cause blackflow out of the skin to inside the injector’s fluid pathway (Hoffman et al., 2001).

Hoffman’s research revealed that despite the fact that there was no needle, there was transference of blood from the patient into the internal components of the jet injector. His research spotlighted the multidirectional flow between the patient and jet injector during the end of the injection process.
Ismach Knew Seriousness of Hepatitis
In 1959, Ismach was cognizant of the risk and seriousness of hepatitis. He knew that hepatitis could be transmitted by people who appear to have no symptoms. “It is possible for a patient to be a carrier of hepatitis and capable of seriously infecting another patient with the disease, although the carrier himself may show none of the symptoms associated with hepatitis” (Ismach, 1962).

Yet despite acknowledging the asymptomatic features of hepatitis Ismach minimized the risk of such transmission via jet injection. Remember Ismach stated, “the danger of cross-infection is almost completely avoided” (Ismach, 1962).
As Jet Infectors has shown throughout this review, the jet injector became contaminated in number of ways. Whether through contamination upon the nozzle orifice, fluid suck-back, or retrograde flow, it seems slight that this device ever remained sterile. Ismach’s claims to the safety of his invention do not carry any weight and amount to nothing more than puffing statements. The risk of transmitting Hepatitis B and Hepatitis C via jet injectors, including the Ped-O-Jet, is not merely theoretical or biological plausible but was in fact real.

  • (CDC, 1977) CDC. DHEW Memorandum: Informal Quarterly Report of October-December 1977. From: Special Investigations Section (Petersen NJ, Bond WW, Carson LA) to: Deputy Director (Favero MS), Hepatitis Laboratories Division, Phoenix, AZ (unpublished).
  • (DoD, 1967) Department of Defense. Military specification: hypodermic injection apparatus, jet, automatic. Defense Supply Center, Phil-Troop Support / Medical Items of Supply. MIL-H-36505, 12 June 1967.
  • (DoD, 1975) Department of Defense. Military specification: hypodermic injection apparatus, jet, foot operated. Defense Supply Center, Phil-Troop Support / Medical Items of Supply. MIL-H-37084, 11 June 1975.
  • (Hoffman et al., unpublished) Hoffman PN, Abuknesha RA, Andrews NJ, Brito GS, Carrasco P, Weckx LY, Moia LJMP, Silva AEB, Lloyd J. A field trial of jet injector safety in Brazil. (unpublished).
  • (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 immunisation. Vaccine. 16 July 2001;19(28-29):4020-4027.
  • (Ismach, 1962) Ismach, Aaron. “Multi-dose jet injection device.” United States Patent 3,057,349. 9 October 1962. Accessible here.

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Fair Use Notice (17 U.S.C. § 107)

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