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* Failed to protect elderly against one strain of flu
* Officials say underscores the need for better flu vaccines
By Julie Steenhuysen
CHICAGO, Feb 21 (Reuters) - A U.S. government analysis ofthis season's flu vaccine suggests it was effective in only 56percent of people who got the shot, and it completely failed toprotect the elderly against an especially deadly straincirculating during flu season.
The U.S. Centers for Disease Control and Prevention said thefindings underscore the need for more effective weapons in thefight against influenza, which kills between 3,000 to 50,000people a year, depending on the severity of the flu season.
"We simply need a better vaccine against influenza, one thatworks better and lasts longer," CDC Director Dr. Thomas Friedensaid in a statement Thursday.
Experts generally estimate the effectiveness of flu vaccinesto be between 50 percent and 70 percent, but this vaccineappears to have fallen on the low side of that range.
The vaccine did cut the risk of medical visits caused byeither influenza A or influenza B by 56 percent, according tothe study published in the CDC's Morbidity and Mortality WeeklyReport.
It was more effective against influenza B, protecting 67percent of those who were vaccinated, compared to the influenzaA (H3N2) strain, which only protected 47 percent of those.
The protective benefits of against influenza B wereconsistent across age groups. That was not the case with theinfluenza A (H3N2) component of the vaccine, which protected 46percent to 58 percent of people aged 6 months to 64 years, butonly 9 percent of those 65 and older.
The estimates are based on studies of 2,697 children andadults enrolled in the U.S. Influenza Vaccine EffectivenessNetwork during between Dec. 3 and Jan. 19. The CDC said thoseestimates may change by the end of the flu season, when morepeople have been sampled.
Even so, the findings suggest that a large group of elderlypeople, who are consistently the most vulnerable to influenza, were completely unprotected during this year's flu season.
One possible explanation may be that in older individuals,the immune system often produces a less robust immune responseto vaccines, or to any infection.
CDC experts suggested that poor immune response to theinfluenza A (H3N2) component of the vaccine may help explain whythe elderly were not protected, but said the findings "shouldnot discourage future vaccination by persons aged 65 years (orolder), who are at greater risk for more severe cases andcomplications from influenza."
They stressed that flu vaccines remain the best preventivetool available, noting that effectiveness has been known to varybased on a number of factors including virus type, age, theparticular flu season and variations in an individual'simmunity.
"Although it's far from perfect, flu vaccination is by farthe best tool we have to protect from flu," Frieden said.
BETTER VACCINES
Frieden said the U.S. Department of Health and HumanServices as well as pharmaceutical companies are working toproduce better vaccines. Efforts include the use of geneticengineering to develop more potent and more modern flu vaccines,with the hope of ultimately developing a universal flu vaccinethat could protect against all strains of flu. Experts predictthat could be possible within eight to 10 years.
"It's going to be hard but it's well worth the effort,"Frieden said.
Already there are signs of change. In November, the Swissdrugmaker Novartis won U.S. Food and DrugAdministration approval for Flucelvax, a seasonal flu vaccinegrown in animal cell cultures instead of live chicken eggs, aspeedier and more reliable process that could help buildstockpiles in the event of a pandemic.
In December, GlaxoSmithKline won FDA approval for anew seasonal flu shot called Fluarix that protects against fourstrains of seasonal flu instead of three. The announcementfollowed the approval last February of AstraZeneca's four-strain flu nasal spray made by the company's MedImmuneunit. Current vaccines tackled two A strains and one B strain.The quadravalent vaccines will add an additional B strain.
Last month, the FDA approved the first gene-based fluvaccine by privately held Protein Sciences Corp, which usesgenetic engineering to grow portions of the virus in insectcells.
"What we're looking at is really incremental improvements,because if we could make the breakthrough improvements easily itwould have happened already," Dr. Leonard Friedland, vicepresident of clinical and medical affairs for vaccines in NorthAmerica at GlaxoSmithKline, said in a recent interview.
Glaxo's quadravalent vaccine is the first inactivated flushot to include four instead of three strains of flu.
"It was just licensed and will be available for nextseason," Friedland said, noting that flu vaccine giant Sanofi is also in the process of having their inactivatedquadravalent flu vaccine approved.
AstraZeneca's FluMist, a live, attenuated or weakened fluvaccine, will also have a four-strain version available for nextflu season.
Dr. Chris Ambrose, a vice president at AstraZeneca'sMedImmune unit, said the company plans to completely switch tothe four-strain version of Flumist.
Sanofi Spokeswoman Donna Cary said the company has producedflu vaccines for specific age groups, including a high dosevaccine designed to produce a greater immune response in theelderly.
"The next step for the future is to get to the point wherewe don't need to develop a new vaccine every year," Cary said."The main thing we are all looking forward to is the universalvaccine."
