Ask the Mayo Clinic: Whatever happened to 'jet injectors?'

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December 7, 2008 12:08 p.m. PT

Ask the Mayo Clinic: Whatever happened to 'jet injectors?'

Dear Mayo Clinic: I remember we used to get vaccines and other shots using an

air gun, and lots of people could get shots quickly. I haven't seen this done

for a long time. Why? Were problems discovered with that method? It seems that

it would be an efficient way to give flu shots, for instance, in a really short

time.

A: Using an air gun -- also called a jet injector -- is a fast way to deliver

vaccines. But jet injectors were discontinued for mass vaccinations about five

years ago because of possible health risks.

A jet injector uses high pressure to force a vaccine or other medication through

a person's skin. Their speed made jet injectors very efficient, so many people

could be vaccinated quickly. They were often used in the military. Although they

weren't pain-free, jet injectors didn't involve needles. The result was less

discomfort than a needle injection, and they caused less anxiety in people who

were afraid of needles.

In some cases, however, jet injectors could bring blood or other body fluids to

the surface of the skin while the vaccine was being administered. Those fluids

could contaminate the injector, creating the possibility that viruses could be

transmitted to another person being vaccinated with the same device.

Of particular concern were viruses transmitted by blood, such as human

immunodeficiency virus (HIV), hepatitis B and hepatitis C. HIV can lead to

acquired immunodeficiency syndrome (AIDS) -- a chronic, life-threatening

condition caused by damage to the immune system. Hepatitis can cause chronic

inflammation of the liver and lead to serious liver damage.

Greater awareness of these diseases and other blood-borne illnesses led to

increased scrutiny of ways they might be spread. Although no widespread

outbreaks of these diseases were caused by jet injectors, the risk of blood and

body fluid contamination of the equipment made jet injectors no longer

acceptable for vaccinations. Instead, most vaccines now are administered by

needle injection, typically in the arm for adults and in the thigh for children.

In the case of the flu vaccine, another option that became available about three

years ago is a nasal mist. All it takes is one spray in each nostril. It's easy,

quick and painless. No needles are involved.

This method has limitations, though. The nasal spray vaccine contains a low dose

of weakened live virus. If a person's immune system is severely suppressed due

to illness or medical treatment, the live virus could, theoretically, cause the

flu in that person. Also, the flu vaccine nasal spray appears to be less

effective than needle injection (flu shot) in people 50 and older. For these

reasons, the nasal spray is only approved for healthy people ages 2 to 49.

The flu shot is approved for people 6 months and older. Because the viruses in

the flu shot aren't live, it can't cause you to get the flu but it will enable

your body to develop the antibodies necessary to ward off influenza viruses.

Mayo Clinic recommends that everyone get the flu vaccine. Although people tend

to think of influenza as a minor illness, it can cause pneumonia and lead to

hospitalization, particularly in high-risk groups. At particularly high risk for

influenza are all children 6 months to 18 years and everyone older than 50.

Others at increased risk of flu-related complications are pregnant women, people

who have a chronic medical condition such as heart disease, diabetes or asthma,

and anybody whose immune system is compromised.

Unfortunately, about 36,000 Americans die each year as a result of influenza.

So, it's important to get a flu vaccine every year to protect yourself.

The current methods of delivering the vaccine are safe and effective and,

although they aren't as fast as the jet injectors, getting a flu vaccine doesn't

take much time.

Flu season lasts from fall through early spring. The earliest Mayo Clinic

usually sees a flu outbreak is September or October. But about 60 percent of

influenza outbreaks in the U.S. occur after January.

Contrary to popular belief, even if you don't get your flu vaccine by the end of

November, it's not too late. The majority of outbreaks occur after that time,

and you can still receive the vaccine as late as March or April.

-- Poland, M.D.,

Vaccine Research Group, Mayo

Clinic, Rochester, Minn.

Medical Edge from Mayo Clinic is an educational resource and doesn't replace

regular medical care. To submit a question, write to: medicaledge@..., or

Medical Edge from Mayo Clinic, c/o TMS, 2225 Kenmore Ave., Suite 114, Buffalo,

NY 14207. For health information visit mayoclinic.com.