JET GUN  INJECTION TRANSMISSION

Potential for cross-contamination from use of a needleless injector.  

A CLINICAL, EPIDEMIOLOGIC AND LABORATORY STUDY ON AVOIDING THE RISK OF TRANSMITTING VIRAL-HEPATITIS DURING VACCINATIONS WITH THE DERMOJET PROTECTED BY AN ANTICONTAMINANT DISPOSABLE DEVICE
 BACKGROUND: Medical devices that are used on patients in fields containing potentially infectious body fluids can become contaminated and transmit infectious agents to other sites on the patient or to other patients if the devices are not properly cleaned and decontaminated after use on each patient treatment site. One such device is the needleless or jet injector, which is widely used in medicine and dentistry to deliver local anesthetic in procedures such as bone marrow aspirations, lumbar punctures, and cutaneous and intraoral injections. This study was conducted to determine whether cross-contamination can occur on in vitro reuse of a needleless injector and whether a manufacturer's recommended method of injector decontamination (ie, immersion sterilization) is effective in the prevention of cross-contamination. METHODS: The study was performed with new autoclaved injectors, fluorescein dye, and Streptococcus crista (the bacteria commonly found in saliva) in the field of use to determine whether these devices can become contaminated during use and carry over the contamination to other sites during immediate reuse. RESULTS: Fluorescein dye and bacteria tests with the needleless injectors showed that contamination or carryover does occur. It appeared to reduced to a minimum when a autoclaved, sterile rubber cap used over the head of the device during injection was replaced between each use, although replacement of the rubber cap alone did not prevent carryover. Immersion of the head of the injector in a 2% glutaraldehyde solution for 30 minutes followed by a sterile water rinse and the replacement of the rubber cap with a sterile cap between uses was shown to curtail bacterial growth and prevent cross-contamination on immediate reuse of the device. CONCLUSION: This study demonstrated that needleless injectors become contaminated during in vitro use and direct contact with contaminated surfaces and that needless injectors carry over the contamination to subsequent sites of release. The replacement of the injector's rubber cap with a new one after initial discharge or the removal of an exposed rubber cap and immersion of the head of the injector in 2% glutaraldehyde followed by a rinse of the head in sterile water, as recommended by one injector manufacturer, can minimize or eliminate the carryover.

UI - 98388286 AU - Weintraub AM AU - Ponce de Leon MP IN - Office of Clinic Management and Patient Services, University of Pennsylvania School of Dental Medicine, Philadelphia 19104-6003, USA. TI - SO - American Journal of Infection Control 1998 Aug;26(4):442-5 AB -

  Jet injectors may transmit  blood-borne infections 

VACCINE 1997 JUN;15(9):1010-1013 - Author: DIMACHE G, CANTACUZINO INST, BACTERIAL VACCINES LAB, SPLAIUL INDEPENDENTEI 103,POB 1-525, BUCHAREST 70100, ROMANIA 

A CLINICAL, EPIDEMIOLOGIC AND LABORATORY STUDY ON AVOIDING THE RISK OF TRANSMITTING VIRAL-HEPATITIS DURING VACCINATIONS WITH THE DERMOJET PROTECTED BY AN ANTICONTAMINANT DISPOSABLE DEVICE

Jet injectors may transmit blood-borne infections, such as hepatitis B virus (HBV) and human immunodeficiency virus (HIV). To evaluate the safety of an anticontaminant disposable device which protects the jet injector apparatus, 22714 healthy subjects were intradermally, inoculated (38162 inoculations) with a variety of vaccines. All the subjects were systematically followed-up clinically and epidemiologically for 6-18 months after inoculation; blood samples from 1619 subjects, before and 60-75 days after inoculation, were examined by enzyme-linked immunosorbent assay (ELISA) for HBV, hepatitis C virus (HCV) and HIV. Before vaccination 212 (13.09%) subjects were positive, 204 positive for HBV markers and eight for the HCV marker. None of the subjects were positive for the anti-HIV marker. During the clinico-epidemiological surveillance and the laboratory investigations mentioned above no clinical viral hepatitis B or C case and no seroconversion to positivity for HBV or HCV markers among the susceptible persons in the group were reported Considering That in similar situations there is a theoretical risk of transmission as high as 1 per 388 to 1 per 3367 injections and that in our case 38162 inoculations were performed in 22714 subjects with the same Dermojet protected by the same type of anticontaminant disposable device, no contamination risk being reported the conclusion can be reached that jet injectors can be safely used in the medical practice if they are protected by the sterile anticontaminant disposable device.  (C) 1997 Elsevier Science Ltd. 

An outbreak of hepatitis B associated with jet injections in a weight reduction clinic.

From January 1984 through November 1985, 31 clinical cases of hepatitis B occurred among attendees of a weight reduction clinic (clinic 1). Before the onset of illness, each case-patient had received a series of injections of human chorionic gonadotropin administered by jet injectors at clinic 1. Clinical history, risk factor assessment, serologic evaluation, and review of clinic injection records were obtained on 287 (84%) of 341 persons who had attended clinic 1 in the first 6 months of 1985. Of this cohort, 21% (60/287) had evidence of acute infection with hepatitis B virus (either documented clinical cases or antibody to hepatitis B core antigen, IgM positive). Of persons who had been given human chorionic gonadotropin at the clinic during the period studied, 24% (57/239) of those receiving human chorionic gonadotropin only by jet injector experienced acute hepatitis B virus infection. None of the 22 persons who had received injections only by syringe experienced hepatitis B virus infection. Stopping the use of the jet injectors on July 2, 1985, at clinic 1, was associated with the termination of this outbreak.

This investigation demonstrated that jet injectors can become contaminatedwith hepatitis B virus and then may be vehicles for its transmission.

Author:
Canter J, Mackey K, Good LS, Roberto RR, Chin J, Bond WW, Alter MJ, Horan JM, Address: Division of Field Services, Centers for Disease Control, Atlanta, GA 30333. Abbreviated Journal Title: Arch Intern Med
Date Of Publication: 1990 Sep Journal Volume: 150 Page Numbers: 1923 through 1927 

Cost of tetanus toxoid injection using a jet-injector (Imule) in collective immunization in Senegal: comparison with injection using a syringe and resterilizable needle

 Sante 1999 Sep-Oct 9:5 319-26Schlumberger M, Châtelet IP, Lafarge H, Genêt A, Gaye AB, Monnereau A, Sanou C, Diawara L, Gueye Y, Lang J           

Needle-less jet injectors were developed by the US army after World War II. Their principal use, however, has been in the administration of lyophilized vaccines from multidose vials to at-risk populations in developing countries. In 1983, a hepatitis B epidemic occurred among customers of a beauty clinic in California (USA) following the use of jet-injectors, demonstrating a clear risk of cross-contamination associated with this technique. As a result, the WHO and Unicef stopped recommending jet-injectors for collective immunizations in developing countries. To eliminate the risk of contamination, Pasteur Mérieux Sérums et Vaccins (now Aventis Pasteur) developed, in 1990, jet-injectors for use with single-use vaccine cartridges. These injectors were tested for tetanus toxoid, DTP, influenza, hepatitis A and typhoid Vi vaccination. The immunogenic reaction was as strong and the injection as well tolerated as for injections using a standard needle and syringe. The additional cost of the Imule technique was evaluated in a district-wide (127,000 inhabitants) tetanus toxoid immunization program at Velingara, Senegal in 1993. The total cost was estimated to be 1.51 FF (76 F CSA, 0.32 US dollars) for one dose of tetanus vaccine given by needle and syringe and 2.41 FF (121 F CSA, 0.56 US dollars) for one dose given by Imule. Thus, the additional cost of injection by ImuleTM was 0.90 FF (45 F CSA, 0.21 US dollars). The cost of cross infection in sub-Saharan Africa has been estimated to be 2.37 FF (118 F CSA, 0.55 US dollars) per injection if injection practices are not supervised. Therefore, the Imule technique may be considered to be cost-effective. However, the technique is still not completely reliable, as shown by the total breakdown of four jet injectors during this vaccination session. Lyophilized vaccines have also not been tested in the field. Vaccinators prefer Imule, training is easy and immunization can be carried out on a day-to-day basis with no vaccine wastage. Imule is not yet in mass production, which would reduce costs. In the face of the ever-increasing risk of cross-contamination during vaccination sessions in sub-Saharan Africa, the Imule technique deserves considerable attention. Author Address Association aide Médecine Préventive (AMP), 28, rue du Dr-Roux, 75724 Paris Cedex 15, France.  

Virus transmission by subcutaneous jet injection. 

J Med Microbiol 1985 Dec;20(3):393-7Brink PR, van Loon AM, Trommelen JC, Gribnau FW, Smale-Novakova IR 

An animal model was used to establish the risk of transmitting a virus infection by subcutaneous jet injection. Virus transmission was studied with mice chronically infected with LDH virus. The virus infection was transmitted by subcutaneous jet injection in 16 cases out of 49. Other routes of cross-infection were ruled out. Before using the jet injector as a harmless instrument for mass subcutaneous injection, further experiments on the risks of virus transmission should be performed.  

[Voen Med Zh 1994 Jul;(7):38-9, 79Evstigneev VI, Lukin EP

The analysis of literature doesn't give strong confirmation that jet injection could provoke the transmission of the infection. Nevertheless such infection is possible because of retrograde flow of vaccine preparation which just has mixed with tissue liquid of a previous patient or taking into account a continuous contact of an injector head with patient's skin during injection. The design of the injector head has a certain significance on this matter. These risk factors can be eliminated by strict observation of rules for handling these instruments. It's necessary to conduct additional experimental researches to prove or refute the safety of jet injections.

Liver 1987 Jun 7:3 163-8Kiyosawa K, Gibo Y, Sodeyama T, Furuta K, Imai H, Yoda H, Koike Y, Yoshizawa K, Furuta S 

Abstract
Six hundred and fifty-one patients with acute viral hepatitis were identified serologically between January 1976 and December 1985. Of these, 109 (17%) had hepatitis A, 135 (21%) had hepatitis B, and 407 (62%) had hepatitis non-A, non-B. The possible infectious causes for acquisition of viral hepatitis occurring within 6 months before the onset of hepatitis were analysed. Approximately 80% of cases of hepatitis A and 70% of hepatitis B had no known risk factor, while in 67% of cases of hepatitis non-A, non-B possible risk factors for infection were documented. Infectious causes for hepatitis A were ingestion of raw shellfish (11%) and previous familial contact with patients with hepatitis A (10%). For hepatitis B, risk factors included medicare (24%), such as transfusion, surgical operation, accidental needle stick and acupuncture, and sexual contact (6%). For hepatitis non-A, non-B, the most important infectious cause was medical procedures (65%). The numbers of hospital employees were 2 (2%) with hepatitis A, 15 (11%) with hepatitis B and 14 (3%) with hepatitis non-A, non-B. These data suggest that hepatitis non-A, non-B can be a kind of nosocomial disease.

Injector.Annette M. Weintraub, MS, DMD, MSEd, MBA Manuel Ponce de Leon; Philadelphia, Pennsylvania

Materials and Methods Results

Discussion and Conclusion

Background: Medical devices that are used on patients in fields containing potentially infectious body fluids can become contaminated and transmit infectious agents to other sites on the patient or to other patients if the devices are not properly cleaned and decontaminated after use on each patient treatment site. One such device is the needleless or jet injector, which is widely used in medicine and dentistry to deliver local anesthetic in procedures such as bone marrow aspirations, lumbar punctures, and cutaneous and intraoral injections. This study was conducted to determine whether cross-contamination can occur on in vitro reuse of a needleless injector and whether a manufacturer’s recommended method of injector decontamination (ie, immersion sterilization) is effective in the prevention of cross-contamination.

Methods: The study was performed with new autoclaved injectors, fluorescein dye, and Streptococcus crista (the bacteria commonly found in saliva) in the field of use to determine whether these devices can become contaminated during use and carry over the contamination to other sites during immediate reuse.

Results: Fluorescein dye and bacteria tests with the needleless injectors showed that contamination or carryover does occur. It appeared to be reduced to a minimum when an autoclaved, sterile rubber cap used over the head of the device during injection was replaced between each use, although replacement of the rubber cap alone did not prevent carryover. Immersion of the head of the injector in a 2lutaraldehyde solution for 30 minutes followed by a sterile water rinse and the replacement of the rubber cap with a sterile cap between uses was shown to curtail bacterial growth and prevent cross-contamination on immediate reuse of the device.

Conclusion: This study demonstrated that needleless injectors become contaminated during in vitro use and direct contact with contaminated surfaces and that needleless injectors carry over the contamination to subsequent sites of release. The replacement of the injector’s rubber cap with a new one after initial discharge or the removal of an exposed rubber cap and immersion of the head of the injector in 2% glutaraldehyde followed by a rinse of the head in sterile water, as recommended by one injector manufacturer, can minimize or eliminate the carryover. (AJIC Am J Infect Control 1998;26:442-5)

Any medical or dental device that comes in contact with nonsterile human body fluids can retain contamination from these fluids. The use of these devices during the subsequent treatment of patients can result in transmission of microorganisms, and possibly infection, from the internal or external surfaces of the instruments to these patients. A basic premise of infection control, established around this potential for cross-contamination, calls for the thorough decontamination of previously used devices before their future application to intact or nonintact human tissues. Numerous instruments and many types of equipment that are used in the care of medical and dental patients have been studied to determine the extent to which they can be contaminated and how effectively and through what methods their decontamination can be achieved.1

Recent investigations have examined devices such as endoscopes,2,3 dental handpieces and attachments,4,5 dental operatory unit water lines,6,7 and ventilator equipment.8,9 One device that never has been studied for its cross-contamination potential and an acceptable method of decontamination after use is the needleless or jet injector. It is used in medicine and dentistry to deliver needleless anesthesia in procedures such as nasal septal and rhinoplastic surgery,10 bone marrow aspiration, biopsies,11 suturing of skin lacerations,12 digital blocks,13 and intraoral soft tissue surgery, exodontia, and application and removal of orthodontic arch bars and ligature wires.14 No cross-contamination complications of repeated in vivo use of the needleless injector have been reported by numerous investigators. 11,15-20 However, none of the studies included the actual microbiologic contamination of the device immediately after use on patients or contact with contaminated body fluids and the potential of the device to transmit any retained microorganisms during subsequent use after various types of decontamination procedures that are recommended by manufacturers. The purpose of this study was to do this under in vitro testing conditions.

MATERIALS AND METHODS

Fluorescein and bacterial indicator tests The needleless injector tested for cross-contamination potential in this study was the Syrijet Mark II Needleless Injector (National Keystone Products Company, Cherry Hill, NJ) (Fig 1).

Fig. 1. The needleless injector used in this study (Syrijet Mark II Needleless Injector, National Keystone Products Company, Cherry Hill, NJ).

[figure 1 omitted]

It is a self-contained instrument that consists of 3 major components: (1) the handle, which primarily contains a bayonet assembly that assists in loading an anesthetic cartridge into the unit and a spring-driven piston impellent that rapidly forces the anesthetic into tissue when it is released11-14; (2) the cartridge well; and (3) a conical injector head with a 0.006-in diameter orifice that accelerates and directs the anesthesia into the site. A rubber cap is applied to the unit’s injector head to serve as a cushion between the device and the patient’s tissue. The head and orifice are the proposed sources of direct cross-contamination in this study.

Fluorescein dye indicator solution and Streptococcus crista, the bacteria commonly found in saliva, were used to evaluate the cross-contamination potential of the jet injector. Sponge pads moistened with 0.5 mL of fluorescein (251 µg/mL) in Xero-Lube (Colgate Palmolive, Canton, Mass.), a saliva substitute, served as the initial contact and discharge media for 6 autoclaved needleless injectors. Two of the injectors were tested without rubber caps, 2 with sterile rubber caps, and 2 with sterile caps that were changed after the initial injector discharge and before subsequent injector discharges. To determine whether fluorescein contamination of the heads and orifices occurred as a result of the first discharges, the 6 injectors were photographed under ultraviolet light. Possible carryover of the contamination was tested by subsequently making 5 consecutive discharges of each of the 6 used devices onto filter pads; these also were photographed under ultraviolet light. Six other autoclaved needleless injectors, configured with or without sterile rubber caps as described previously, were subjected to the same initial discharges onto fluorescein-containing sponge pads but then were discharged separately into 6 consecutive enzyme-linked immunosorbent assay dilution tubes. From each of the 36 tubes, 0.2 mL aliquots of liquid were transferred to enzyme-linked immunosorbent assay plates and the optical density of fluorescein on the plates was read at 490 nm on a BIO-TEK Reader (BIO-TEK Instruments, Inc., Winooski, Vt) to quantitatively determine fluorescein carryover after the initial discharges of the injectors. The concentration of fluorescein on each plate was determined from a standard fluorescein curve developed in the study, plotting absorbance (y-axis) versus fluorescein concentration (x-axis).

Injector cross-contamination tests performed with S crista bacteria were done to determine the qualitative carryover potential of the devices to both brain-heart infusion (BHI) agar and broth, the ability of an immersion sterilant to decontaminate injector heads after bacterial contamination and before reuse, and the effect of the use of a sterile rubber cap on bacterial carryover.

Nine autoclaved injectors were used in one bacteria test. Three served as controls and had initial discharges onto sterile sponge pads moistened with 0.1 mL sterile water. Three uncapped injectors were discharged initially onto sponge pads moistened with 0.5 mL of a suspension of S crista, grown to a density of 1 × 108 bacteria/mL, and then touched to either BHI agar or injected into BHI broth. Three other uncapped injectors also were discharged onto sponge pads containing S crista but were immersed just past their heads in 2% glutaraldehyde (Procide, Biotrol International, Louisville, Colo) for 30 minutes, rinsed in sterile water, and dried with sterile towels before their contact with BHI agar or injection into BHI broth. This decontamination method is recommended by one needleless injector manufacturer.

All inoculated BHI agar plates and broth tubes were incubated overnight at 37°C (98.6°F) and observed and labeled “ ” or “-” for bacterial growth.

A second series of cross-contamination tests with S crista was performed to determine the effect of the injector’s rubber cap on bacterial carryover after the unit’s initial bacterial exposure. In these tests, 12 injectors with sterile rubber caps were discharged onto sponge pads containing S crista and then touched to BHI agar or injected into BHI broth. Twelve other capped injectors were managed the same, but had caps replaced with new, sterile caps before inoculation onto BHI agar or broth and subsequent incubation and reading. To enhance the statistical validity of these tests, they were repeated with 16 rather than 12 injectors.

RESULTS

Ultraviolet photographic results of fluorescein dye tests of needleless injector contamination after initial discharge exposure demonstrated that contamination occurred on the head and rubber cap components. Carryover of fluorescein to subsequent injection sites also was evident from filter pad contamination on at least the first of five discharge sites. This carryover existed regardless of the presence of the rubber cap on the injector head, although replacement of the rubber cap after initial exposure minimized fluorescein cross-contamination. Quantitative evidence of fluorescein carryover after the needleless injector’s initial exposure is shown in Table 1. [table omitted]

Injectors with or without rubber caps demonstrated carryover of fluorescein; cap replacement again resulted in cross-contamination minimization.

Injector tests with S crista showed that the heads were contaminated with the bacteria after exposure at initial discharge and that the contamination was carried over by 1 subsequent discharge onto agar plates or into broth tubes. An injector manufacturer’s recommended immersion of the injector heads without caps into 2% glutaraldehyde for 30 minutes followed by a sterile water rinse and drying in sterile towels was sufficient to eliminate any S. crista that remained after initial exposure.

Tests on the cross-contamination potential of injector rubber caps showed that their presence during initial discharge resulted in 86% (24) of the 28 devices evaluated contaminating subsequent discharge sites with S crista. Replacement of the cap immediately after initial use greatly reduced but did not eliminate bacterial carryover, as exhibited by 11% (3) of the 28 tested injectors.

DISCUSSION AND CONCLUSION

The in vitro fluorescein indicator tests conducted in this study clearly show that needleless injectors become contaminated on use. The contact of the injector’s discharge orifice, head, and rubber cap with surfaces simulating body tissues and fluids during the in vitro tests generally resulted in the contamination of these 3 sites on the device. This was shown in the fluorescein tests in which body fluids, simulated by the fluorescein in Xero-Lube, were seen and photographed on the orifice, head, and rubber cap under ultraviolet light after initial injection discharge of the unit. Although this type of test was not conducted in vivo, we expect that similar contamination of the device would occur during patient use and could be detected with similar fluorescein studies.

Carryover of contamination of the injector from its initial discharge to subsequent injection sites also was demonstrated in these studies. Both fluorescein and bacterial contamination were carried over to sites of at least 1 succeeding discharge of injector units, whether the devices were used with or without the rubber caps. Two actions were shown to minimize or eliminate this carryover: (1) the replacement of the rubber cap with a new one after the injector’s initial discharge and (2) the removal of the exposed rubber cap and immersion of the head of the device in 2% glutaraldehyde followed by a rinse in sterile water, as recommended by one needleless injector manufacturer. The latter activity resulted in the curtailment of bacterial growth and prevention of cross-contamination on immediate reuse of the injector.

On the basis of the study results, we conclude that immersion of the head of a needleless injector (after removal of the rubber cap) that has been exposed to bacterial contamination in 2% glutaraldehyde for 30 minutes followed by a sterile distilled water rinse and the replacement of the cap with a new sterile cap is sufficient to provide a decontaminated instrument for subsequent use. This concurs with 1 decontamination method recommended by a needleless injector manufacturer.

We thank Dr. Gary Cohen of the University of Pennsylvania School of Dental Medicine’s Department of Microbiology for his guidance and support of this project.  

References

1. American National Standard. Good hospital practice: handling and biological decontamination of reusable medical devices. Association for the Advancement of Medical Instrumentation. ANWI/AAMI ST35-1991.

2. Rutala W, Clontz E, Weber D, Hoffmann KK. Disinfection practices for endoscopes and other semi-critical items. Infect Control Hosp Epidemiol 1991;12:282-8.

3. McCracken JE. Endoscopy reveals debris, fluid, and damage in patient-ready GI endoscopes. Infect Control Sterilization Technol 1995;1(6):32-43.

4. Lewis DL, Boe RK. Cross-infection risks associated with current procedures for using high-speed dental handpieces. J Clin Microbiol 1992;30(2):401-6.

5. Mills SE, Kuehne JC, Bradley DV. Bacteriological analysis of high-speed handpiece turbines. J Am Dent Assoc 1993;124:59-62.

6. Mayo JA, Oertling KM, Andrieu SC. Bacterial biofilm: a source of contamination in dental air-water syringes. Clin Prevent Dent 1990;12(2): 13-20.

7. Whitehouse RLS, Peters E, Lizotte J, Lilge C. Influence of biofilms on microbial contamination in dental unit water. J Dent 1991;19:290-5.

8. Cefai C, Richards J, Gould FK, McPeake P. An outbreak of Acinetobacter respiratory tract infection resulting from incomplete disinfection of ventilatory equipment. J Hosp Infect 1990;15:177-82.

9. Gauthier DK, Long M. Colonization of mechanical ventilation bags during use. AJIC Am J Infect Control 1994;22:358-66.

10. Wolff L. Jet spray in nasal surgery. Arch Otolaryngol 1971;93:327-9.

11. Hardison CD. Application of a versatile instrument for production of cutaneous anesthesia without needle penetration of the skin. J Am Coll Emerg Physicians 1977;6:266-8.

12. Mumford DM, Jackson PL. The successful use of jet anesthetic injections with childhood lacerations. Clin Pediatr 1976;15:872-4.

13. Ellis GL, Owens A. The efficacy and acceptability of using a jet injector in performing digital blocks. Am J Emerg Med 1993;11:648-50.

14. Greenfield W, Karpinski YF. Needleless jet injection in comprehensive pain control and applications to oral surgery. Anesth Progr 1972;19(4):94-7.

15. Schmidt DA. Jet injection: high speed infiltration anesthesia. J Dent Child 1970;37:459-62.

16. Epstein S. Pressure injection of local anesthetics: clinical evaluation of an instrument. J Am Dent Assoc 1971;82:374-7.

17. Santangelo RG. Rapid, “painless” local anesthesia. J Pediatr 1973;82:736.

18. Mott MG. The use of the Syrijet to attain local anaesthesia in children with acute leukemia. Br J Clin Pract 1973;27:415-6.

19. Smith KA, Stockman JA, Stuart MJ, Oski FA. Jet injection anesthesia—a technique for painless bone marrow aspiration [letter]. J Pediatr 1974;85:731-2.

20. Dyment PG, Doering EJ, McHugh MJ. Safety and efficacy of jet anesthesia for bone marrow aspirations. Blood 1978;52(3):578-80.

From the University of Pennsylvania School of Dental Medicine, Philadelphia. 
 

A model to assess the infection potential of jet injectors used in mass immunisation.

Hoffman PN, Abuknesha RA, Andrews NJ, Samuel D, Lloyd JS.

Laboratory of Hospital Infection, Central Public Health Laboratory, 61 Colindale Avenue, London NW9 5HT, UK. phoffman@phls.org.uk

Jet injectors are needleless injectors that penetrate skin with high-pressure fluid. They have potential advantages over needles and syringes in mass immunisation programs, but concerns over their capacity to transfer blood-borne viruses have been a barrier to acceptance. Hepatitis B infection can transmit in 10 pl of blood; detection of such low volumes presents severe difficulties to such assessments. A model to assess jet injector safety was developed using injection of an inert buffer into calves and assaying the next injector discharge, representing the next dose of vaccine, for blood using a highly sensitive ELISA. Four injectors were tested: two with reusable heads and direct skin contact, one with single-use injector heads and one where the injector head discharged at a distance from the skin. All injectors tested transmitted significant (over 10 pl) volumes of blood; the volumes and frequency of contamination varied with injector. The source of the contamination was consistent with contamination by efflux of injected fluid and blood from the pressurised pocket in tissue that is formed during injection. This insight should inform the design of safe jet injectors.

PMID: 11427278 [PubMed - indexed for MEDLINE]