Research Documented Fluid Suck-back

During the 1950s, inventors noted the undesirable phenomenon of fluid suck-back in multi-use nozzle jet injectors. Yet despite attempts to resolve the problem, fluid suck-back has been continuously observed and reported upon through-out the past 60-years.

  • Anderson, Lindberg and Hunter (1958) observed a large-scale military field trial conducted upon sailors stationed at Naval Air Station in Norfolk, Virginia. The mass influenza vaccination campaign administered 20,145 injections with a Press-O-Jet injector between 1955 and 1956. Fluid suck-back was observed during the military vaccination campaign. “Another ball valve is located at the rear of the plunger assembly and, if improper seating occurs, will allow vaccine to be returned to the reservoir on each injection,” wrote the researchers.


  • Inventor of the Ped-O-Jet, Aaron Ismach, stated within his 1962 patent 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” (Ismach, 1962). His assertion reveals MUNJIs faced issues with check-valves. Subsequent research has revealed the Ped-O-Jet was no exception to this inherent design fault.


  • In 1977, CDC’s Hepatitis Laboratories Division conducted safety testing on the Ped-O-Jet. The researchers observed a drop of fluid remained on the injector nozzle after firing and would disappear back into the nozzle orifice within 3 to 5 seconds. The researchers concluded, “These manipulations causing disappearance of the fluid drop are common during clinical use of the jet injector” (CDC, 1977).


  • Weniger, Jones and Chen recalled CDC’s 1977 investigation of the Ped-O-Jet, stating, “After injections, they [CDC] observed fluid remaining on the Ped-O-Jet nozzle being sucked back into the device upon its cocking and refilling for the next injection (beyond the reach of alcohol swabbing or acetone swabbing).”


  • In 1994, the CDC retested the safety of the Ped-O-Jet. After artificially contaminating the underbelly of a shaved rabbit with Hepatitis B surface antigen (HBsAg), a sterile Ped-O-Jet was placed upon the site and administered an injection. The subsequent injection was fired into a vial and tested for HBsAg. The results found the ejected fluid of the next shot fired was positive for HBsAg in 19 out of 50 (38%) of the samples (Grabowsky et al., 1994). Cross-contamination of HBsAg from the skin surface to the ejectate of the subsequent shot was due to either fluid suck-back or retrograde flow.


  • The CDC collaborated with American Jet Injector Corporation and the University of Florida to test the safety of the Am-O-Jet, a MUNJI device. The Am-O-Jet was an identical design of the Ped-O-Jet. Within this study the researchers admit the check-valve had been redesigned; thus further implicating the inherent design faults of previous Ped-O-Jet models. It is noteworthy to add, the researchers found rates of contamination were significant with the Am-O-Jet (Sweat et al., 2000).


  • In 1974, Aaron Ismach developed an alternative jet gun injector in which the energy source was generated through hand-power rather than foot-power. Ismach’s patent purported to overcome the risk of fluid suck-back. “The check outlet valve serves to prevent the entry of any air or suck-back of any fluid during the loading cycle of the medicament chamber with the spring pressure on this valve sufficiently light to be easily overcome during the firing or ejecting cycle” (U.S. Patent 3805783).

These reports document that jet injectors—including the most widely used jet injector, the Ped-O-Jet—allowed contaminates upon the nozzle orifice to be sucked into the internal fluid pathway and infect the next dosage to be fired.



  • (Anderson, Lindberg, & Hunter, 1958) Anderson EA, Lindberg RB, Hunter DH. Report of large-scale field trial of jet injection in immunization for influenza. JAMA 167:549–552, 1958.
  • (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).
  • (Grabowsky et al., 1994) Grabowsky M, Hadler SC, Chen RT, Bond WW, de Souza Brito G. Risk of transmission of hepatitis B virus or human immunodeficiency virus from jet injectors and from needles and syringes. Unpublished manuscript draft, dated January 3, 1994.
  • (Ismach, 1962) Ismach, Aaron. “Multi-dose jet injection device.” United States Patent 3,057,349. 9 October 1962.
  • (Sweat et al., 2000) Sweat JM, Abdy M, Weniger BG, Harrington R, Coyle B, Abuknesha RA, Gibbs EP. Safety testing of needle free, jet injection devices to detect contamination with blood and other tissue fluids. Ann NY Acad Sci 2000;916(31):681-682.
  • (U.S. Patent 3805783) Ismach A. “Hand Powered Hypodermic Jet Injector Gun.” United States Patent 3,805,783. 23 April 1974.
  • (Weniger, Jones & Chen) Weniger BG, Jones TS and RT Chen. “The Unintended Consequences of Vaccine Delivery Devices Used to Eradicate Smallpox: Lessons for Future Vaccination Methods.” National Center for Immunization & Respiratory Diseases. [Poster Presentation].


© Shaun Brown and Jet Infectors, 2016 – 2018
Fair Use Notice (17 U.S.C. § 107)


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