NEW YORK, Sep 27 (Reuters Health) -- An experimental vaccine appears to offer wide-ranging protection against the flu, results of a study in mice suggest. The chief advantage of the new vaccine, which has not been tested in people, is that it provides protection against all strains of influenza A, unlike current flu shots, which have to be reformulated each year to battle the season's most common strains of the flu virus.
Current flu vaccines work by targeting one of two types of proteins, hemagglutinin and neuraminidase, that are present on the surface of the flu virus, according to Dr. Walter Fiers, of the University of Ghent in Belgium. But since these proteins often mutate, new strains of the flu develop every year or two, making it difficult to design a vaccine that can protect against all flu strains. Currently, flu shots are effective about 80% of the time.
But, in a study published in the October issue of the journal Nature Medicine, Fiers and colleagues report on a vaccine that targets the M2 protein, which is identical in almost all strains of influenza A, one of the two primary flu types.
When the investigators tested the vaccine on mice, a triple dose of the vaccine was 90% to 100% effective in protecting the rodents from a wide range of influenza A viruses. Six months after the mice were vaccinated, they were still immune to influenza A, according to the report.
The researchers tested two different forms of the vaccine, an injection and a nasal spray. Both were equally effective at producing immunity to the flu.
"In conclusion, we have described a vaccine that provides long-lasting, protective immunity in mice against all influenza A virus strains," Fiers and colleagues write.
But, in an editorial accompanying the study, Dr. Edwin D. Kilbourne of New York Medical College in Valhalla, notes "...it may be premature to herald this vaccine as 'universal.'" He points out that the study included only two influenza viruses, which both had the same M2 protein.
Even though the study shows that the M2 vaccine can offer some protection, Kilbourne notes that certain strains of influenza A do have mutations in the gene for the M2 protein. There is no way to know, from these results, whether the vaccine would protect against those particular strains of the flu, Kilbourne writes.
Noting the ever-changing nature of flu viruses, he concludes, "It seems probable that a combination of old and new approaches -- perhaps 'all of the above', will be required to develop a truly 'universal' vaccine for influenza."
