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Trio of New Strains Chosen For 2008–2009 Flu Vaccine


 

GAITHERSBURG, MD. — All three virus strains in the influenza vaccine for the 2008–2009 season will differ from this year's vaccine, based on a majority vote by an advisory committee to the Food and Drug Administration.

The Vaccines and Related Biological Products Advisory Committee members voted to accept the choices recommended by the World Health Organization for next year's trivalent vaccine: an A/Brisbane/59/2007 (H1N1)-like virus, an A/Brisbane/10/2007 (H3N2)-like virus, and a B/Florida/4/2006-like virus.

These choices represent a notable departure from the flu vaccine formulas of recent years, which have included repeat appearances by the Solomon Islands strain of influenza A.

The change was prompted in part by the rise of the A/Brisbane/10/2007-like strain, which accounted for 82% of the influenza A (H3N2) isolates characterized by the Centers for Disease Control and Prevention between October 2007 and January 2008. According to the most recent data available from the CDC, the H3N2 strain of influenza A has become the dominant strain for this year's flu season.

Although influenza A is causing most of the illness, the well-publicized mismatch between the influenza B virus chosen for this year's flu vaccine and the currently circulating B virus is drawing extra attention. But the lengthy process of developing the flu vaccine and the challenges to produce it in volume and on schedule remain the same each year.

Two types of influenza B circulate every year, and one committee member compared the choice of B virus for each year's vaccine with flipping a coin.

An influenza B virus from the Victoria group was chosen for the 2007–2008 vaccine, but the strain chosen for 2008–2009 is of the Yamagata lineage. The most recent data from the CDC for the 2007–2008 flu season (as of Feb. 9, 2008) showed that 93% of the circulating influenza B viruses in the United States were of the Yamagata lineage, while 7% of the viruses were of the Victoria lineage. “But we have both groups [of influenza B virus] circulating worldwide,” noted Nancy Cox, Ph.D., director of the influenza division at the CDC.

The committee members also discussed the possibility of tailoring future flu vaccines to different populations. Unlike previously vaccinated adults who have been exposed to both types of influenza B over time, children would likely benefit from a vaccine that has strains from both B virus lineages, noted Dr. Robert Couch, professor of molecular virology and microbiology at Baylor College of Medicine, Houston.

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