WRAIR’s 1959 Safety Testing of Military Ped-O-Jet Injector

Jet Injectors = Jet Infectors

March 6, 2016

military jet injector vaccinations

In the late 1950s, Aaron Ismach and Abram Benenson developed a multi-use nozzle jet injection device, which they named the Multi-dose Jet Injection Device. Mr. Ismach was a civilian scientist working for the U.S. Army Medical Equipment and Research Development Laboratory at Fort Totten, New York and Dr. Benenson was a Colonel in the U.S. Army Medical Corps.

The Multi-dose Jet Injection Device was capable of inoculating 1,000 persons an hour. A novel invention for its time. The device allowed for the rapid immunization of a large population. In a military setting the device allowed for the mass immunization of recruits in bootcamps, training facilities and depots.

The device, which was the development of the U.S. military, was tested upon military recruits. Between 1958 and 1959, the efficacy of the Multi-dose was tested in a field trial amongst 1,440 military personnel who were inoculated with a 1 milliliter dose of influenza vaccine within a one hour period (Benenson, 1959). Another source stated the device was field tested upon military personnel at Fort Leonard Wood around 1959-1960 (Army, 2002).

The device was marketed under the name Automatic Jet Hypodermic Injection Apparatus but became more commonly known as the Ped-O-Jet due to later development of a non-electrical foot-pump model or pedal-operated-jet injector.

Multidose Jet Injection Device

1959 Benenson- Mass immunization by jet injection-1

(photo by Benenson, 1959)

Benenson reported on the introduction of this device in his 1959 article Mass Immunization By Jet Injection. In the article, Benenson and his colleagues at Walter Reed Army Institute of Research (WRAIR) had expressed concern of infectious pathogens, such as hepatitis, being transferred via the newly invented Multi-dose Jet Injector. The concern arose from the researchers’ observation of “occasional bleeding” during the jet injection. Bleeding at the injection site was reported within 5 to 10 percent of the injections.

Benenson also reported,

when it [bleeding] does occur, the blood continues to ooze staining the shirt, perhaps because infiltration of vaccine into the tissue interferes with normal clotting mechanism. This bleeding is simply controlled by applying pressure for a short period of time with a pledget of absorbent cotton. Increased bleeding and immediate wheal formation are found with incorrect orifice design. When the injector is not held firmly so that the tip moves while vaccine is being discharged, the skin can be cut; this is minimized by proper technique, a dry skin and a roughened surface on the jet nozzle.

The researchers reported two safety tests conducted upon the Multi-dose Jet Injector (Ped-O-Jet):

1) A precipitin test was conducted after a Multi-dose Jet Injector administered 762 injections without replacing or cleansing of the nozzle. The researchers reported,

The problem of hepatitis has been minimized. After each of the five different injection sessions, with no cleansing of the nozzle between a total of 762 recipients, the nozzle was soaked in saline and then precipitin tests were set up with rabbit and horse antihuman serum. The results were negative, indicating the presence of less than 15 gammas of human serum, if any (emphasis added) (Benenson, 1959).

For those of us who do not know, a gamma is an out-dated term for a unit of measurement. François Cardarelli (2003) explains in the Encyclopedia of Scientific Units, a gamma is a unit of measure of mass equal to one microgram (1µg).

Benenson reported, “the presence of less than 15 gammas of human serum” on the nozzle of the Multi-dose Jet Injector (Ped-O-Jet) after administering 762 injections. 15 gammas of human serum equates to 15 micrograms.

To put this into perspective based upon advances in modern science, in 1984 Feinman and colleagues reported the minimum volume of blood capable of transmitting the hepatitis B virus to be 10 picoliters (Feinman et al., 1984).

In a 2013 interview, I asked Dr. Peter Hoffman, an epidemiologist at the United Kingdom’s Health Protection Agency, how much blood would be required to transmit the hepatitis C virus? Hoffman responded,

There is a greater knowledge base on hepatitis B than hepatitis C in this area. It is generally assumed that hepatitis C is about 10-times less infectious than hepatitis B. This means hepatitis C having a transmission volume starting at around 100 picolitres, but it is probable that a greater volume would usually be required (Hoffman, 2013).

Interesting, yet remember these values are still microscopic. Since my interview with Dr. Hoffman in 2013 the transmissibility rates of viral hepatitis are still unknown and are left to professional opinion.

In doing the math, 15 micrograms converts to 0.015 microliters, or rather 15,000 picoliters. Therefore, this 15 gammas of human serum is capable of holding 1,500 hepatitis B particles and 150 hepatitis C particles.

The National Institute of Health has helped us comprehend these figures. In response to my inquiry on the topic the NIH stated,

a picoliter is 10-12 or one trillionth the size of a liter…to put this in perspective, if a drop of blood were a microliter in volume, it would look no bigger than a period on this page. A picoliter would be a million times smaller (NIH, 2013).

2) Possible transmission via the Multi-dose was also assessed in a laboratory investigation. The researchers administered a saline injection with a Multi-dose to a hog “at the peak of the viremia of hog cholera,” and then subsequently injecting a healthy hog. The results were unable to detect any contamination using the assays available during that era (Benenson, 1959). Weniger, Jones, and Chen said of this investigation that the “military [was] unable to detect surrogates for viral agents in assays available in that era.” The science of the late 1950s could not detect contamination within such microscopic levels, and most importantly, no tests existed to detect viral hepatitis, which was still not well understood during this era.

Herein, the most widely used jet injector within the United States military was noted for “occasional bleeding,” whereupon the “the problem of hepatitis” could only be “minimized” and not eliminated. Interesting wordage—problem of hepatitis. Not “risk” of hepatitis. Problem. Herein Benenson acknowledges that transmission via the Multi-dose (Ped-O-Jet) was possible.

Although this study reported no cross-contamination, the study was blind to the later advancements science procured. HCV was discovered in 1989. The transmissibility rate of HBV was discovered in 1984. The unit of measurement known as a picoliter, which is roughly a million times smaller than a period on this page, was recognized in 1960.

Upon further review, it could have been possible for serum hepatitis to have been transmitted in the amount of blood reported during the administration of the Multidose Jet Injector in Benenson’s 1959 report.


  • (Army, 2002) Department of the Army. Army Medical Department Profiles: Brig. Gen. Frank Allen Ramsey. June 2002. pg. 52.
  • (Benenson, 1959) Benenson AS. Mass immunization by jet injection. In: Proceedings of the International Symposium of Immunology, Opatija, Yugoslavia, 28 September—1 October 1959 (International Committee for Microbiological Standardization, Secton of the International Association of Microbiological Societies). Zagreb: Tiskara Izdavackog zavoda Jugoslavenske akademije; 1959;393–399 [Library of Congress QW 504 I60p 1959].
  • (Cardarelli, 2003) François Cardarelli (2003). Encyclopedia of Scientific Units, Weights and Measures. Springer-Verlag London Ltd. ISBN 978-1-4471-1122-1.
  • (Feinman et al., 1984) Feinman SV, et al. DNA: DNA hybridization method for the diagnosis of hepatitis B infection. J Virol Methods 1984;8(3):199-206.
  • (Hoffman, 2013) Hoffman, PN. Personal communication. February 28, 2013.
  • (NIH, 2013) National Institute of Health. Personal Communication. September 4, 2013.
  • (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.

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