BETHESDA, MD. — A federal advisory panel unanimously voted to change two of the three strains slated to comprise the 2006–2007 influenza vaccine.
The Food and Drug Administration's Vaccines and Related Biological Products Advisory Committee recommended the changes based on shifts seen in viral activity, according to data culled from surveillance sites in Japan, England, Australia, and the United States.
The recommended vaccine changes correlate with the World Health Organization's suggested vaccine composition for the Northern Hemisphere for the 2006–2007 winter season.
The FDA advisory panel recommended that the trivalent vaccine retain the influenza A(H1N1) strain—A/New Caledonia/20/99(H1N1)-like virus—due to evidence of continued resilience.
However, they suggested replacing the A/California/7/2004(H3N2)-like virus with A/Wisconsin/67/2005(H3N2)-like virus. Also, the influenza B/Shanghai/361/2002-like virus should be replaced with the B/Malaysia/2506/2004-like virus.
According to Dr. Zhiping Ye, senior investigator for the division of viral products with the FDA's Center for Biologics Evaluation and Research, influenza A infections were inadequately covered by the 2005–2006 vaccine. It's estimated that in the pediatric population there was an overall 50% reduction in the hemagglutination inhibition (HI) reaction to the H3N2 component of the vaccine.
A similar reduction in coverage of the A/Wisconsin strain was noted in adult populations in Europe, Japan, and the United States.
“If we use Wisconsin as a vaccine, then we probably will get better coverage,” Dr. Ye said. “But this is only one piece of the puzzle.” Surveillance studies show that several other strains in the same lineage as A/Wisconsin also were inadequately covered by the current vaccine. However, there would likely be residual coverage of these strains by targeting the A/Wisconsin strain.
The current vaccine still appeared effective against the influenza A(H1N1) strain, A/New Caledonia/20/99(H1N1)-like virus, according to data from surveillance sites in North and South America, Europe, Asia, Africa, and Australia.
Data from the United States and Europe showed that several strains were inadequately covered by the influenza B component of the current vaccine, and the B/Malaysia/2506/2004-like virus was one of them, Dr. Ye noted.
The vote on the 2006–2007 vaccine composition was unanimous, but the panel members had some reservations.
Although influenza A strains are responsible for most U.S. influenza cases, in recent years the selection of an influenza B strain has been more difficult to accurately pin down. “This winter the B/Victoria has been dominant in North America, but our vaccine was the B/Yamagata strain,” said panelist Dr. Robert B. Couch, professor of medicine, microbiology, and immunology at Baylor College of Medicine, Houston.
“We do the best we can to predict the likely epidemic virus, but for roughly the last 3 years, it's been a little too much of a guess with the influenza B. If it's going to continue this way, then we need to discuss how to address this problem,” Dr. Couch said in an interview.
Despite these misgivings, he voted in favor of the B/Malaysia strain, which is part of the B/Victoria/2/87 lineage.