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Updated Vaccine Needed for Mutated Flu Viruses

Posted on: Monday, 18 February 2008, 00:00 CST

The World Health Organization (WHO) recommended last week that next year’s flu vaccine be updated to reflect changes in the three most common influenza viruses.

The report corroborates findings from the U.S. Centers for Disease Control and Prevention (CDC) that the viruses have mutated and made the current flu vaccines less effective.

The WHO said similar reports from health agencies around the world have also reinforced the need for a new vaccine.

The organization reported that H1N1 viruses in 18 countries had developed mutations that made them resistant to Tamiflu, currently the best treatment for flu.  Resistance to the older drugs amantadine and rimantadine is now so common that their use is no longer recommended.

Although less effective than in typical years, this year’s flu vaccine can still protect people against the most serious effects of the infection, according to the CDC.

Flu vaccines contain the three most common circulating strains, usually two "A" strains and one "B" strain.  However, influenza viruses constantly mutate, and health experts meet throughout the year to monitor the viruses and determine how to best formulate the vaccine .

Because the vaccines are made using a time-consuming process involving chicken eggs, the process must begin several months before the next flu season starts.  During that time the WHO begins advising companies that make the vaccine, and governments that purchase them, about which three flu strains would best protect the general population.

"As in previous years, national control authorities should approve the specific vaccine viruses used in each country," the WHO said, according to a Reuters report.

In an average year up to half a million people worldwide are killed by the flu.  Last week’s CDC weekly flu report said forty-four states had widespread flu activity, and ten children had died from the illness.

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On the Net:

Additional information about influenza can be found at:

http://www.who.int/csr/disease/influenza/en/ and http://www.cdc.gov/flu/

Source: redOrbit Staff and Wire Reports

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