FDA panel endorses new B strain for 2009-10 flu vaccine

Feb 18, 2009 (CIDRAP News) – A US Food and Drug Administration (FDA) advisory committee today recommended that pharmaceutical companies use one new influenza strain, the B component, in next season's flu vaccine.

The Vaccines and Related Biological Products Advisory Committee voted to follow the lead of the World Health Organization (WHO), which last week recommended replacing the influenza B strain in this year's vaccine, which is from the Yamagata lineage, to one from the Victoria lineage, said Karen Reilly, an FDA spokeswoman. The WHO and the FDA panel recommended that the two influenza A strains for the Northern Hemisphere remain the same.

Reilly told CIDRAP News that the votes on retaining the current influenza A/H1N1 and A/H3N2 strains were unanimous. However, the vote on changing the influenza B strain was 14 to 0 with one abstention.

The flu vaccine is reformulated each year in an attempt to match ever-evolving virus strains. The WHO and FDA recommend the strains for the vaccine in February, allowing companies enough time to grow the viruses in chicken eggs and process them into vaccine doses. Most years the vaccine is protective, but last flu season all three strains in the vaccine were a poor match for circulating viruses, and the WHO and FDA recommended changing all three strains for this season.

The influenza B component of this year's flu vaccine was from the Yamagata lineage, but the proportion of strains from the Victoria lineage continues to increase and has become predominant in many countries, including the United States.

The WHO and now the FDA committee recommend the following for next season's vaccine:

• For the H1N1 component, a strain similar to A/Brisbane/59/2007
• For the H3N2 component, a strain similar to A/Brisbane/10/2007
• For the B component, a strain similar to B/Brisbane/60/2008-like virus, replacing B/Florida/4/2006

Reilly said the committee discussed recommending the addition of a second B strain to the vaccine, but did not vote on the measure. Health officials in the United States have discussed including both lineages in the seasonal vaccine to address the unpredictable circulation of the influenza B strains, given that a vaccine against one lineage offers little protection against the other.

Some of the committee members said there was not enough research yet to support adding a second B strain lineage, she said.

See also:

Feb 13 CIDRAP News story "WHO picks new B strain for 2009-10 flu vaccine"

Jan 16 CIDRAP News story "Experts consider 4-strain flu vaccine to fight B viruses"