U.S. flu season worsens as new vaccines ordered

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U.S. flu season worsens as new vaccines ordered

Fri Feb 22, 2008 8:41 PM GMT

By Maggie Fox, Health and Science Editor

WASHINGTON (Reuters) - Influenza is widespread in 49 states, and this

year's epidemic has killed at least 22 children, the U.S. Centers for

Disease Control and Prevention reported on Friday.

On Thursday the U.S. Food and Drug Administration agreed to completely

change next year's flu vaccine mix because all three strains included

in the flu shot cocktail have mutated. But companies have a head start

on working with two of the three, the CDC's Dr. said.

FDA advisers agreed with the World Health Organization recommendations

made last week on changing the vaccine to match the drifting flu viruses.

" In brief, seasonal influenza activity has increased during the past

week, " told reporters in a telephone briefing.

Flu has killed 22 children so far this season, said. She did not

have details on any of the cases.

said the CDC was watching the epidemic and asking state health

departments to collect data on who gets sick, whether the were

vaccinated, and whether influenza drugs were effective in fighting the

infections.

Several European countries have reported that people are becoming

infected with strains that resist the effects of Tamiflu, the

antiviral drug made by Roche AG and Gilead Sciences.

said the CDC had seen little evidence that flu was resisting

Tamiflu in the United States. " We have actually seen antiviral

resistance only sporadically in eight states, " she said.

And there are reports that some people who have become ill with

confirmed flu did get vaccinated.

The flu was also found in Florida, but the CDC said it had not become

widespread.

FRESH COCKTAILS

Flu vaccines contain a mixture of two influenza " A " strains, which

currently are types known by the shorthand of H3N2 and H1N1, and a " B "

strain. These mutate or " drift " a little each year, which is why the

vaccine must be formulated freshly each season.

This happens in the late winter or early spring in each hemisphere --

February in the Northern Hemisphere and September in the Southern.

" We would say based on our laboratory data that the match is not

optimal both for the H3N2 component of the vaccine and also for the

influenza B component, " told reporters in a telephone briefing.

" In Europe they have primarily had influenza A H1N1. Data generated in

Europe indicate that strains circulating there are not so well-matched

with the vaccine. "

The vaccines still help prevent serious disease, said, even if

they do not completely prevent infection.

Last year officials were already ready to change the H3N2 vaccine and

labs have been working to make a type that could be easily made into

vaccine, so they have a head start, said.

It takes months to make a batch of vaccine. Samples of virus must be

injected into carefully cultivated fertilized eggs and then grown.

Some strains grow well in eggs and others do not, so it is months

before companies know how much vaccine they will have to sell for the

upcoming season.

Five companies make flu vaccine for the U.S. market -- Sanofi Pasteur,

Australia's CSL Ltd, GlaxoKline Plc, Novartis AG and nasal spray

maker MedImmune, recently acquired by AstraZeneca Plc.

Next week the CDC's Advisory Committee on Vaccine Practices will meet

and discuss whether to expand recommendations for who gets influenza

vaccine. Currently the vaccine is advised for all children between 6

months and 5 years old, people over 50, those with chronic illnesses

and pregnant women.

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