FRIDAY, May 30, 2003 (HealthDayNews) -- For all you needle phobics who hate to get your annual flu vaccine, how does the prospect of a once-in-a-lifetime shot sound?
A prototype vaccine developed by researchers at the Wistar Institute in Philadelphia, delivered not by injection but by nasal spray, worked well in animal studies. The researchers suspect it may prove effective for several flu seasons.
If further research bears fruit, there's a chance for the same kind of vaccine for humans, the scientists say.
Their approach was to target a protein within the flu virus that doesn't mutate as often as others.
"Current vaccines target two proteins [within the flu virus] that mutate frequently," says Laszlo Otvos Jr., an associate professor of chemistry at the Wistar Institute and a co-author of the report, published in the June 2 issue of Vaccine.
For that reason, public health officials are always faced with the problem of updating the vaccine so it will protect against the virus that's expected to be prevalent in an upcoming flu season.
But the Wistar researchers focused instead on the M2 protein, which is a more stable protein portion of influenza viruses that mutates less frequently.
The experimental vaccine includes an engineered peptide built by Otvos that mimics this M2 protein. The vaccine, in nasal spray form, was given to the mice twice. After they received it, a steep rise in antibodies to M2 was found in blood samples, and the mice resisted replication of the virus in their respiratory tracts.
Those mice that got the M2 protein had much less virus in their respiratory tracts than those who didn't get it, Otvos says.
The mice also had a more powerful antibody response to the engineered vaccine than to infections by the flu virus itself, the researchers found.
Every year, about 114,000 people in the United States are hospitalized with influenza, a viral respiratory infection, according to the U.S. Centers for Disease Control and Prevention (CDC). About 20,000 people die because of it, most of them elderly. While the flu vaccine is not 100 percent effective, if you get a flu shot you're likely to be far less sick than without it, the CDC says.
Of the new vaccine, Dr. James C. King, a professor of pediatrics at the University of Maryland School of Medicine, says, "The idea is wonderful." His research focuses on live, intranasal vaccines.
"People have been talking for years about using some of the internal proteins [such as the M2] within the virus that don't mutate as fast" to make a vaccine, he says.
What makes the Wistar research exciting, King adds, is the scientists were not only able to make the mice's immune systems recognize the M2 protein pieces, but "the mice made antibodies and it also protected them from symptoms."
As exciting as the research is, King offers a caveat: "It's a good five to 10 years -- minimum -- before we'll see this in humans."
Otvos agrees it will take time to answer some important questions, such as: Are antibodies against M2 enough to protect you from the flu? Is the response long-term? Will subsequent flu strains have a mutated M2 structure?
If it all bears out, he says, the flu vaccine may become a once-in-a-lifetime preventive measure.
More information
For myths and facts on flu shots, see the U.S. Centers for Disease Control and Prevention's National Immunization Program. For information on the flu virus vaccine, check the U.S. Food and Drug Administration.
