Why Compressed Air Isn't a Go-To for Vaccination Anymore
Written on
Vaccines represent one of humanity's most significant advancements in public health, transforming many deadly diseases into manageable conditions. Yet, the experience of receiving a vaccine often leaves much to be desired.
While some may experience temporary side effects post-vaccination, a more universal discomfort lies in the method of administration—needles. The sharpness and intimidating appearance of needles often provoke anxiety. Wouldn't it be better to receive a vaccine without the piercing sensation of a needle?
Enter the jet injector, a needle-free vaccination method that has been around since the early 20th century. Despite its advantages, the World Health Organization currently advises against its widespread use. What’s behind this caution, and how does this innovative method work?
From Diesel Engines to Vaccination
The concept of jet injectors was inspired by the mechanics of diesel engines, which require fuel to be atomized and mixed with air to function effectively. A fuel injector achieves this by expelling a high-speed mixture through a narrow nozzle, creating tiny droplets.
In 1935, mechanical engineer Arnold Sutermeister observed that if these injectors could accidentally inject diesel fuel into skin, they could intentionally deliver medicinal doses as well. Thus, the jet injector was born, using high pressure to deliver concentrated medicine directly into the arm, making it particularly useful for large vaccination campaigns, as it eliminated the need to change needles between patients.
Jet injectors gained prominence from the 1950s to the 1970s, notably in the U.S. Army for vaccinating recruits and in campaigns to immunize children against polio and smallpox. This method played a significant role in eradicating smallpox.
However, despite their historical success, why are jet injectors not a standard feature in clinics today?
The Downsides of High-Pressure Vaccination
Jet injectors are not without their complications. They face three primary issues: splash-back, suck-back, and retrograde flow.
Splash-back occurs when the injected liquid splatters off the skin, contaminating the nozzle and potentially the internal components of the injector. This contamination risk can lead to unintended cross-vaccination.
Example: A patient receiving a flu vaccine with a jet injector may inadvertently receive remnants of that vaccine when the next patient receives insulin.
Suck-back happens when blood or other fluids on the nozzle are drawn back into the injector. This can contaminate subsequent doses, as the injector must be pressed directly against the skin and may draw blood upon insertion.
Example: If a patient with HIV is vaccinated, their blood could be sucked back into the injector and injected into the next person.
Retrograde flow describes the scenario where the injected medication mixes with bodily fluids and is subsequently drawn back into the nozzle. This issue combines the risks of both splash-back and suck-back.
Example: In the mid-1980s, a weight-loss clinic’s use of jet injectors led to hepatitis B infections due to contamination.
Consequently, while jet injectors were designed for efficient mass vaccination, these contamination risks necessitate thorough cleaning between uses, leading to delays.
But what about individual use? Unfortunately, jet injectors are often reported to be more painful than traditional needle injections. Military recruits who received vaccinations using jet injectors reported significant pain, and any movement during administration could result in severe skin damage.
Due to these concerns, in 1997, the U.S. Department of Defense discontinued the use of jet injectors for mass vaccinations.
The Current Landscape of Needle-Free Vaccination
Today, jet injectors—now referred to as “needle-free injectors”—are still in limited use but are unlikely to replace traditional needle injections anytime soon. Some modern designs include disposable cartridges to address contamination concerns but generate more waste.
The InsuJet, available in the U.K. and parts of Europe, offers needle-free insulin delivery, allowing for faster absorption without cross-contamination risks. However, studies show that pain levels are comparable to those of traditional needles.
Overall, improvements in needle design—such as the use of smaller gauge needles and more effective vaccine formulations—make needle-based injections less painful. As a result, jet injectors are likely to remain specialized tools rather than mainstream solutions.
In Summary: The Drawbacks of Needle-Free Vaccination
Jet injectors emerged from the discovery that high-pressure liquids could penetrate the skin. They have proven effective for vaccination but pose risks of cross-contamination if not cleaned properly. While they saw extensive use in the latter half of the 20th century, safety concerns have led to their decline.
Even without needles, jet injectors can still cause discomfort. Current advancements in disposable needles mean that jet injectors will likely remain niche products, overshadowed by improved traditional vaccination methods.
Have you ever experienced a needle-free injection? What was your experience like?
If you enjoyed this article, consider sharing it on Twitter and tagging @swestreich with your thoughts.
Not yet a paid Medium member? Consider joining to read unlimited articles and support my writing at no additional cost to you:
Join Medium with my referral link — Sam Westreich, PhD