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When it comes to the flu vaccine, is a shot in the arm worth two squirts in the schnoz?

Flu shot circa 1976
CDC Archive Photo
A public health clinician administers a flu vaccine in this 1976 photo from the Centers for Disease Control. Will a new nasal spray make needles as outdated as leisure suits?

 

Like countless other Minnesotans, I have an allergy to sharpened steel — particularly when it is driven deep into my upper arm in the form of a flu shot.

Which is why I have to ask the question, "Why isn't everyone getting FluMist, the nasal spray form of influenza vaccine?"

It certainly works well for kids, where studies have consistently shown FluMist to be more effective than the traditional, sharpened steel vaccine (let's call that FluSteel). The New England Journal of Medicine published the most recent comparison study, where researchers enrolled nearly 8,000 children ages 6 months to 5 years and gave half of them a shot in the arm with FluSteel, and the other half a couple of squirts in the nose with FluMist.

Vaccination is never 100 percent effective because flu viruses are forever altering their appearance, but both FluMist and FluSteel appeared to ward off the flu in more than 90 percent of cases. Still, the traditional vaccine had about twice as many treatment failures (FluSteel recipients who got the flu anyway) as FluMist, and that's nothing to sneeze at.

Why do kids do better with spray?
Studies vary, but in teenagers and adults, FluMist and FluSteel seem to be equally effective. Why FluMist offers greater protection to kids than adults is a source of speculation, but the difference may be that the two vaccines are, well, different.

Keep in mind that a vaccine is a way of presenting the human immune system with a "Wanted" poster for a particular virus or bacteria. Your immune system looks at the picture of the assailant, then manufactures antibodies designed specifically to kill "Influenza Larry" or "Suzie Smallpox." For influenza, each vaccine is actually a collection of "Wanted" posters, the highlight reel of the major players in last year's flu season.

The manufacturing process for both FluMist and FluSteel begins the same way, by incubating and growing viruses in live chicken eggs (which is why someone with an egg allergy should avoid vaccination). Traditional vaccine manufacturers take these viruses and kill them by chopping them up into a million (or so) pieces.

To produce FluMist, the viruses are simply maimed and incapacitated; they are alive and capable of limited reproduction but are incapable of causing an infection. This is what is termed a "live attenuated virus." In this way, vaccines like FluMist are able to present the body's immune system with a fairly intact "Wanted" poster. In contrast, FluSteel's poster looks like a 3-year-old went after Influenza Larry's likeness with a pair of scissors: recognizable in parts, but fragmented.

Location, location, location
FluMist's performance advantage also may have something to do with location. Snorting a vaccine may do a better job of stimulating the antibodies that line the nose and respiratory tract, which is where Influenza Larry does his bidding before franchising his progeny throughout the entire body. (There are no case reports of an influenza strain capable of boring a hole two inches into the human shoulder muscle. Yet.)

These schnoz antibodies might explain why FluMist outperforms FluSteel in kids, but draws even in adults. Once inside the nose, the FluMist virus must replicate enough times to trigger an appropriate immune response. The more it replicates, the stronger the immune response. That seems to work well in flu-naive kids, but the pre-existing flu antibodies that most adults have might keep the FluMist virus from replicating enough to stimulate the robust immune response seen in kids.

Not for everyone
Of course FluMist is not for everyone, say, people who are allergic to diminutive nasal syringes, or elderly men with nasal hair as dense as furnace filters. A strong asthma history raises concern because the immune response that FluMist stimulates in the nose and respiratory tract can trigger wheezing.

There's also a concern that people living with someone whose immune system has been weakened (by HIV, immune-suppressant drugs or chemotherapy, etc.) could pass along the FluMist virus to their housemates. The worry is that with no immune system to stop it, the crippled vaccine virus could cause a symptomatic infection. "So far, that's an entirely theoretical concern," noted Dr. Frank Rhame, a Twin Cities' infectious disease specialist with expertise in the treatment of HIV.

The U.S. Food and Drug Administration also hasn't approved FluMist for people with "a medical condition that places them at high risk for complications from influenza" — such as chronic heart or lung problems, diabetes or kidney failure. The makers of FluMist excluded anyone with chronic health problems from their initial licensing studies, so the vaccine can't be FDA-approved for those people.

Similarly, studies with FluMist did not include enough patients older than age 49 to determine if they respond differently from younger people. Which means that people 50 and older are stuck with FluSteel.

Spray is mercury-free
One thing FluMist has going for it is that it doesn't now and never did contain thimerosal, the notorious mercury-containing vaccine preservative that has been studied for possible connections to autism. I'm no fan of mercury ingestion, and I'm glad to see it go, but I say notorious because we've blown through millions of research dollars proving again, and again, and yet again, that thimerosal doesn't cause autism, and that's money that could be used to study, well, autism.

No needle. No thimerosal. Covers ages 2 to 49. Better protection in children, equal coverage in adults. FluMist might well provide more protection in the sense that more people (needle-phobes, unite!) will actually get vaccinated. So why aren't we all getting FluMist?

Familiarity for one. Traditional vaccines like FluSteel are tried and tested, and they make up the bulk of the available vaccine. If everyone wanted FluMist, there wouldn't be nearly enough to go around. For now, FluMist remains the hopeful rookie, with some impressive stats that might or might not hold up over time.

It also could have to do with — brace yourself — money. The flu vaccination letter my wife and I got from our pediatrician's office said, "Your pediatrician will help determine which type of vaccine is best for you and your child." Age and health restrictions aside, that used to be code for "your insurer may decide what vaccine is best for you."

Until recently, FluMist was twice as expensive as the traditional FluSteel and many insurers didn't cover it. According to Jill Marette at the Minnesota Department of Health's Immunization Program, the cost of FluMist is down to $18 compared to FluSteel's $14. "Most of the major insurers now cover FluMist, but individuals should check if they want to be sure," Marette cautioned.

No excuses: Get vaccinated
Be it snort or steel, there are plenty of reasons to get yourself and your offspring vaccinated: misery, mortality and, yes, money. Influenza absenteeism is undeniably expensive. Lying miserable and catatonic on the couch does nothing for our nation's GDP; neither does taking the day off to tend to a sick child.

Influenza season is upon us: Act now while supplies last.

Dr. Craig Bowron is a Twin Cities internist and writer.

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