Flu hits U.S. early

vaccine misses main virus

CDC officials still hopeful shots will lessen epidemic

November 18, 2003|By NEW YORK TIMES NEWS SERVICE

The influenza vaccine now being given was not developed to protect against a strain of the virus that has surfaced in this country this fall, but the government is optimistic that it will stave off outbreaks, a top federal health official said yesterday.

Animal studies suggest that the strains of virus included in the vaccine are close enough to the new one that the vaccine will give some protection, said the official, Dr. Julie L. Gerberding, the director of the Centers for Disease Control and Prevention.

Still, she warned, the United States could face a severe epidemic this year, given that the flu season began unusually early and has hit Texas and Colorado particularly hard.

"It's a little too early to say whether or not this portends the worst flu season we have had in a long time," Gerberding said in a telephone news conference.

Her agency is responsible for tracking and controlling infectious diseases.

She said she was "sounding the alarm" to urge more people to get flu shots to "nip this problem in the bud." The center does not know how many people have received flu shots this season. "People have the impression we are doing better this year than last year, but we do not have the data to back that up," she said.

The flu vaccine includes three strains of influenza virus, but it was not designed to protect against a new one that has appeared in a number of countries over the past year. It is known as the Fujian strain, a variant of the Panama strain that is included in the current vaccine.

Both are categorized as H3N2 strains that have been linked to higher rates of serious illness requiring hospital care and death, Gerberding said.

Each year, influenza causes 114,000 hospital admissions and 36,000 deaths in the United States, the CDC says.

The flu virus mutates frequently. Health officials change the strains of virus put in the flu vaccine each year as they try to keep up with mutations. But matching strains in the vaccine with those circulating among humans in flu season is notoriously unpredictable.

The World Health Organization committee that makes the recommendations for the flu vaccine knew about the Fujian strain in February, said Dr. Klaus Stoehr, an influenza expert at the organization.

But Stoehr said in a recent interview that the committee decided not to include the Fujian strain because scientists could not make it pure enough in time for a human vaccine.

The flu vaccine is prepared in hen eggs. Decisions about the components of the vaccine have to be made months in advance in part because manufacturers and farmers need to know how many eggs to prepare in anticipation of demand.

Influenza typically occurs in winter in each hemisphere, and the vaccines are prepared at different times. The vaccine being prepared for use in the Southern Hemisphere will include the Fujian strain, Stoehr said.

"There may be less than optimal protection against H3N2" in the Northern Hemisphere, "but no vaccine failure has been reported," he said.

Gerberding said it was common for the circulating influenza to gradually change genetically - known as "drift" - as it spreads to infect more people.

Tests at the center found that 84 percent of the 55 strains of influenza virus isolated this fall are the Fujian strain.

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