Experts Expect Flu Vaccine To Match This Season's Viruses

Kate Traynor

WASHINGTON, DC 25 September 2008—As the influenza season gets under way, federal health officials say they believe that this season's vaccine formulation will protect those who receive it.

"We are optimistic that this year's vaccine will be on target in protecting against the flu this coming season," said Daniel B. Jernigan, deputy director of the Influenza Division at the Centers for Disease Control and Prevention (CDC).

Jernigan, speaking yesterday from Washington, D.C., at the National Foundation for Infectious Diseases annual media briefing on influenza, said the optimism reflects data on influenza strains circulating in the Southern Hemisphere, where the annual flu season is ending.

"Viruses that they’re seeing right now do match those that are in the [U.S.-licensed] vaccine this year," Jernigan said.

Influenza vaccine formulations used in the United States during the 2007–08 flu season were not well matched to circulating viruses, according to CDC. The agency reported that the influenza type B strain in the formulation differed antigenically from 98% of type B viruses characterized CDC, and the H3N2 strain differed from 77% of circulating H3N2 viruses. The H1N1 component of the vaccine matched 66% of circulating H1N1 viruses.

According to a preliminary analysis, last season's vaccine was 44% effective overall for the prevention of laboratory-confirmed influenza, CDC stated.

Three new viral strains were selected for the 2008–09 U.S. influenza vaccine formulation. Manufacturers began announcing as early as August that their influenza vaccines were available for shipment, and some health care providers have already announced or started holding vaccine clinics for patients.

CDC Director Julie L. Gerberding said yesterday that up to 146 million doses of influenza vaccine will be available this season.

For the first time ever, all healthy children age six months through 18 years—about 30 million people—are on the list of populations targeted for influenza vaccination. With this addition, influenza vaccination is recommended for about 85% of the U.S. population.

As in past years, CDC is emphasizing the need for health care workers to get vaccinated to prevent them from becoming ill and from spreading the virus to patients.

"I think it's unconscionable for health care workers who don’t have a medical contraindication to not receive the flu vaccine," Gerberding said. "It's that important to themselves and to the patients that they serve."

Gerberding declined to predict how active this influenza season is likely to be.

"We absolutely have no way of knowing what the season will look like," she said.