GAITHERSBURG, MD. — The 2007–2008 trivalent influenza vaccine should retain two strains from the current vaccine and change one strain, a Food and Drug Administration advisory panel has concluded.
The Vaccines and Related Biological Products Advisory Committee followed the lead of the World Health Organization, which made its recommendations for a Northern Hemisphere winter vaccine a week earlier.
In most cases, the FDA follows its panel's advice.
The decision gives the green light to manufacturers to go ahead with production. It generally takes until July or August for vaccine makers to complete testing, acquire FDA approval, and begin packaging their product.
Distribution usually starts in September and ends by Nov. 1.
Based on surveillance reports, the availability of seed stock to grow viruses, and reagents to test potency, vaccine makers already had begun production of most of the strains that ultimately were selected, said Albert Thomas, a Sanofi Pasteur representative who spoke at the FDA meeting. The manufacturers take the early production risk in order to speed up the process, he explained.
If the FDA committee had chosen different strains, vaccine makers likely would have had to reduce their ultimate production by 20%, Mr. Thomas said.
That potential production loss pushed the committee to vote against changing one component, the influenza A (H3N2) strain, even though the most recent surveillance data suggest that a different H3 strain currently is emerging.
The WHO recommended keeping the current H3N2 strain, which is the A/Wisconsin/67/2005-like virus. The 2006–2007 flu season had been dominated mostly by influenza A (H1N1) strains, said Nancy J. Cox, Ph.D., director of the Centers for Disease Control and Prevention's influenza division. But in February, it appeared that H3N2 strains were starting to dominate. It wasn't clear yet which of those might be the predominant H3 strain, Ms. Cox said.
Even though panelists were concerned about the emergence of a new H3N2 subtype, 11 of 13 members voted to keep the current H3 strain. “At this point, I feel like we don't have any choice,” said Dr. Melinda Wharton, deputy director of the CDC's National Immunization Program and a temporary voting member of the committee. She noted that manufacturers already had started production on the current H3 strain.
Two committee members said they wanted to defer a decision until more surveillance data were available.
The panel voted unanimously to change the current H1N1 strain from A/New Caledonia/20/99-like virus with A/Solomon Islands/3/2006. The WHO had recommended that change.
The FDA committee also voted unanimously to retain the current B strain—B/Malaysia/2506/2004-like virus—mirroring the WHO recommendation.
The 2006–2007 season has been fairly mild, Ms. Cox said. As of Feb. 17, widespread flu activity was reported in 24 states, 14 states reported regional activity, 10 reported local activity, and 2 reported sporadic activity.
For adults, the death rate from pneumonia and influenza—at 6.9%–-was below the epidemic threshold of 7.9%. There were 3 pediatric deaths during that week, bringing the total to 15 deaths since the season began Oct. 1, 2006.