CDC Evaluates the Risk of Multi-Use Nozzle Jet Injectors

Following the 1996 CDC/WHO conference, CDC continued to evaluate and engage in discussions on the risks of multi-use nozzle jet injectors (MUNJI). The timeline below shows the reports, conferences, and one collaborative study in which CDC investigated MUNJI devices. The timeline also shows a shift in CDC’s stance on jet injectors, from viewing MUNJI devices being permissible in dire situations to MUNJI’s being inherently unsafe and discouraging their use altogether.

1999 CDC Reports MUNJIs Pose Medium Risk in a JAMA article
In a 1999 Journal of the American Medical Association article by Rebecca Voelker is the revelation that the CDC viewed jet injectors with a reusable nozzle that was not swabbed between patients as a medium risk for cross-contamination (Voelker, 1999).
Therefore, even before the publishing of subsequent research on jet injector safety which demonstrated it did not matter if the nozzle was swabbed or unswabbed (i.e., Hoffman et al., 2001; Hoffman et al., unpublished; Sweat et al., 2000), the CDC viewed MUNJIs as a medium risk.

1999 Voelker - Eradication Efforts Need Needle-Free Delivery- CDC Diagram- Reusable nozzle is a medium risk

(Voelker, 1999)

2000 Am-O-Jet Fails Safety Test
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 had an identical design to the Ped-O-Jet. This study tested the potential for cross-contamination via the Am-O-Jet amongst calves and pigs. The design of the study replicated previous in vivo jet injector studies (Sweat et al., 2000). Dr. Bruce Weniger of the CDC and coauthor of the study stated, “We have detected contamination well above currently [sic] levels that we would consider indeterminate or uninterpretable” (FDA, 1999). In other words, the researchers found the rates of contamination were significant.

2002 (Feb. 8) CDC Report – General Recommendations on Immunization
CDC urged the use of MUNJI devices to be limited only in dire situations and when other, safer methods are not viable. The report stated,

Efforts are under way for the research and development of new high-workload JIs using disposable-cartridge technology that avoids reuse of any unsterilized components having contact with the medication fluid pathway or patient’s blood…the use of existing multiple-use-nozzle JIs should be limited . . . [and] considered when the theoretical risk for bloodborne disease transmission is outweighed by the benefits of rapid vaccination with limited manpower in responding to serious disease threats (e.g., pandemic influenza or bioterrorism event), and by any competing risks of iatrogenic or occupational infections resulting from conventional needles and syringes… (CDC, 2002).

CDC’s shift to dire use only was a minuscule step forward from the agency’s warning eight-years prior, which noted if jet injectors became contaminated there is a risk for disease transmission (CDC, 1994).

2002 (Sept 16) CDC & WHO Meeting – Consultation on MUNJI Safety Evaluation
CDC and WHO hosted a meeting at CDC Headquarters in Atlanta to discuss the safety of MUNJI devices. Amongst the invited attendees were WHO, CDC, FDA, USAID, PATH, International Vaccine Institute, and members of academia. During this time, the CDC endorsed the use of MUNJI devices in dire situations until disposable-cartridge jet injectors became standardized (Weniger, 2005).

2004 (March 30) WHO & CDC Meeting – Consultation on MUNJI Safety Evaluation
WHO and CDC hosted a subsequent meeting on jet injector safety at WHO Headquarters in Geneva, Switzerland. The goal of this meeting was to establish criteria for a new generation of jet injector devices. The attendees attempted to answer several important questions relating to the matter of cross-contamination. Questions such as: “How infectious is blood? How do we measure it? How do you model the risk? What level of risk is acceptable?” (FDA, 2005).

The attendees were in agreement that a fraction of a picoliter can transmit infection. This conclusion was far different from the previous, widely-accepted yet unofficial belief that Hepatitis B is transmissible in 10 picoliters of blood or greater (FDA, 2005).

The attendees deemed it was inappropriate to make health officials decide what was an “acceptable” level of risk from using MUNJIs (Weniger, 2005). The objective of the health industry is not to contemplate risk but to sustain life and improve health.

The attendees questioned the relevance of prior animal models and recommended all future jet injector safety trials use human HBsAg carriers and the most sensitive PCR assays for detecting contamination within ejectates (Weniger, Jones & Chen). The use of Hepatitis B surface antigen (HBsAg) was not purely to assess if Hepatitis B is transmissible via jet injection but to use HBsAg, a highly infectious pathogen, as a threshold in evaluating safety. The idea being if a highly infectious pathogen is transmissible than that model of jet injector is unsafe.

Most importantly, during this meeting the CDC finally decided to abandon its attempt in developing safer MUNJI devices and discouraged the use of all MUNJI devices under any circumstance (Weniger, 2005).

2004 (May 25-26) Seventh Annual Conference on Vaccine Research
Dr. Bruce Weniger, of CDC, summarized the downfall of MUNJI devices within his poster presentation at the Seventh Annual Conference on Vaccine Research. Dr. Weniger wrote, “The U.S. military withdrew them [MUNJIs] in 1997, and WHO and CDC now caution against their use” (Weniger, 2004).

2004 (June 8-10) WHO Conference – Fifth Global Vaccine Research Forum
At WHO’s Proceedings of the Fifth Global Vaccine Research Forum, Dr. Weniger again stated the risks and hazards of multi-use nozzle jet injectors. “Subsequent bench studies of it [Med-E-Jet] and the more common Ped-O-Jet indicated that their nozzles could become contaminated with hepatitis B virus and pose a risk for transmission between consecutive vaccines” (WHO, 2005).

2005 MUNJIs Are “Inherently Unsafe”
Dr. Bruce Weniger, of the CDC, believed MUNJIs were inherently unsafe.

MUNJIs are inherently unsafe. Their re-use without intervening sterilization of fluid pathways which may be exposed to patient blood or tissue fluid violates established principles that apply to other critical medical devices.

One cannot rely of the absence of documented cases of disease transmission beyond the California outbreak.

It is unlikely that routine post-marketing surveillance would link sporadic cases to prior MUNJI use (Weniger, 2005).

2006 (Dec. 1) CDC Report – General Recommendations on Immunization
CDC reported disposable-cartridge jet injectors overcame the risks of cross-contamination posed by MUNJIs. “In the 1990s, a new generation of JIs was introduced with disposable cartridges serving as dose chambers and nozzle. With the provision of a new sterile cartridge for each patient and correct use, these devices avoid the safety concerns for multiple-use-nozzle devices” (CDC, 2006a).

2006 CDC Report – Needle-free Intradermal Influenza Study
CDC stated MUNJIs are “inherently unsafe.”

Safety concerns arose over multi-use-nozzle jet injectors (MUNJIs)…which use the same nozzle to inject consecutive patients without intervening sterilization. A hepatitis B outbreak in the mid 1980s caused by one MUNJI as well as other published and unpublished studies of this and other devices, indicated blood and tissue fluid containing pathogenic agents could be transmitted among patients. This led to discontinuation and recommendations against their use in public health, and market removal in 1997 of the most common device, the Ped-O-Jet®.

Since the 1990s, a new generation of safer disposable-cartridge jet injectors (DCJIs) have appeared. DCJIs avoid the inherently unsafe design of MUNJIs, since the disposable cartridge has its own sterile orifice and nozzle and is discarded between patients (CDC, 2006b).

2011 (Jan. 28) CDC Report – General Recommendations on Immunization
CDC reiterates the risks and hazards of jet injectors.

Jet injectors that use the same nozzle for consecutive injections without intervening sterilization were used in mass vaccination campaigns from the 1950s through the 1990s; however, these were found to be unsafe because of the possibility of bloodborne pathogen transmission and should not be used (CDC, 2011).

1999 – 2006 CDC’s Needle-Free Injection Technology Webpage
From 1999 to 2006, the CDC had an entire webpage devoted to needle-free injection technology. Although the site,, has since been long taken down. The webpage once provided links to reports from international and government health agencies containing information about the risks and hazards of jet injectors and links to Department of Defense websites that detailed the withdrawal of the devices by one manufacturer and the discontinuation of their use by the military. Fortunately through this webpage along with a substantial number of its reports were archived. CDC’s jet injector webpage can be accessed here.

CDC discouraged the use of multi-use nozzle jet injectors only after a protracted investigation and numerous meetings. CDC first investigated the safety of jet injectors in 1977, and actively investigated MUNJI devices from 1993 to 2004. Their ultimate decision, to discourage MUNJI use under any circumstance, was long overdue considering their partners at the WHO discouraged the use of MUNJIs six-years earlier.

It is important to note that although up until 2004 the CDC endorsed the use of MUNJIs in dire emergencies, the devices had not actually been used in a mass vaccination campaign within the United States. MUNJIs were last used in public in 1997 during a meningitis outbreak at Michigan State University (Paneth et al., 2000) and within the U.S. military on December 9th of 1997 (DoD, 1997). Whereas the WHO was quick to abandon MUNJI technology, the CDC wished to keep the devices as a contingency plan. It is my opinion that the agency’s reluctance to abandon the technology was ill-considered as it delayed the inevitable and prevented any seroepidemiological studies on prior MUNJI use.

Unequivocally, CDC’s jet injector studies demonstrated MUNJIs pose a risk in transferring blood-borne pathogens between patients. Since 2004, CDC has viewed MUNJIs as “inherently unsafe,” and has repeatedly discouraged their use.

Yet to date, CDC Headquarters in Atlanta has never listed multi-use nozzle jet injectors as a risk factor in transmitting blood-borne pathogens, even despite the high prevalence of Hepatitis C amongst those who had the greatest exposure to mass jet injector inoculations—Vietnam era veterans.


  • (CDC, 1994) Centers for Disease Control and Prevention. General Recommendations on Immunization: Recommendations of the Advisory Committee on Immunization Practices (ACIP). Morb Mortal Wkly Rep 43:(RR-1):7–8, 1994.
  • (CDC, 2002) Centers for Disease Control and Prevention. General Recommendations on Immunization: Recommendations of the Advisory Committee on Immunization Practices (ACIP) and the American Academy of Family Physicians (AAFP). Morb Mortal Wkly Rep February 8, 2002;51 (No. RR-2): 1-35.
  • (CDC, 2006a) Center for Disease Control and Prevention. Recommendations of the advisory committee on immunization practices-(ACIP). Morb Mortal Wkly Rep. 55:(RR-15), 2006.
  • (CDC, 2006b) Centers for Disease Control and Prevention. Needle-free Intradermal Influenza Study. CDC-ISO-4785. 5 March 2006.
  • (CDC, 2011) Centers for Disease Control and Prevention. Recommendations of the Advisory Committee on Immunization Practices-ACIP. Morb Mort Wkly Rep. Vol. 60. No. 2. 28 Jan. 2011.
  • (DoD, 1997) Memorandum: Jet Hypodermic Injection Units. Philadelphia: Defense Logistics Agency. 9 December 1997.
  • (FDA, 1999) Food and Drug Administration. General Hospital & Personal Use Devices panel: open session. Department of Health and Human Services Meeting. Rockville, MD. 2 August 1999.
  • (FDA, 2005) FDA. General Hospital and Personal Use Devices Panel of the Medical Devices Advisory Committee. August 9, 2005. 35th Conference. Washington, D.C.
  • (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.
  • (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).
  • (Paneth et al., 2000) Paneth N, Kort EJ, Jurczak D, Havlichek DA Jr, Braunlich K, Moorer G, Vanderjagt D, Sienko D, Leiby P, Gibbons C. Predictors of vaccination rates during a mass meningococcal vaccination program on a college campus. J Am Coll Health. 2000 Jul;49(1):7-11.
  • (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.
  • (Voelker, 1999) Voelker R. Eradication Efforts Need Needle-Free Delivery. JAMA May 26, 1999;281(20):1879-1881.
  • (Weniger, 2004) Weniger BG. Trends, challenges and opportunities for jet injection technology (presentation). National Foundation for Infectious Diseases. Seventh Annual Conference on Vaccine Research. 25-26 May 2004. Arlington Virginia.
  • (Weniger, 2005) Weniger B. Safety of Multi-use-nozzle Jet Injectors (MUNJIs) for Bloodborne Pathogen Cross-contamination (draft). Conference Notes. 7 August 2005.
  • (Weniger, Jones & Chen) Weniger BC, Jones TS, & Chen RT. The Unintended Consequences of Vaccine Delivery Devices Used to Eradicate Smallpox: Lessons for Evaluating Future Vaccination Methods.
  • (WHO, 2005) WHO. Proceedings of the Fifth Global Vaccine Research Forum. WHO/IVB/05.09. 2005.

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