Next season’s influenza shots to contain two newer strains
■ Of the three to be included in the 2012-13 vaccine, one is being used in this season’s immunization.
Amid reports that influenza cases across the United States are beginning to rise, infectious diseases experts are preparing for the next flu season.
A Food and Drug Administration advisory committee on Feb. 28 selected the three influenza virus strains that will make up the nation’s 2012-13 flu vaccine. They are the same viruses that the World Health Organization recommended be used in flu vaccines administered throughout the Northern Hemisphere.
Among those strains is an A/California/7/2009 (H1N1)-like virus, which is used in the 2011-12 influenza vaccine. An A/Victoria/361/2011 (H3N2)-like virus and a B/Wisconsin/1/2010-like virus (Yamagata lineage) also will be included.
In deciding the immunization’s composition, infectious diseases experts “test tens of thousands of influenza isolates throughout the world and characterize them at different levels to try to make the best determination of whether to maintain the same viruses [in the flu vaccine] or change them,” said Pedro A. Piedra, MD, professor in the Dept. of Molecular Virology and Microbiology and the Dept. of Pediatrics at Baylor College of Medicine in Houston. “It’s always a best guess that is made” of what influenza strains will be circulating the next year, he said.
Selecting the proper influenza B virus strain to include in the vaccine is particularly difficult, because two lineages of the B virus circulate in the U.S., Dr. Piedra said. That is one reason many infectious diseases experts support the use of a quadrivalent influenza vaccine, which could include two influenza A virus strains and two B strains, Dr. Piedra said.
In February, the U.S. got one step closer to having such a vaccine when the FDA approved MedImmune’s FluMist Quadrivalent vaccine for use in people ages 2 to 49. It is the first quadrivalent influenza vaccine the agency has approved.
“Illness caused by influenza B virus affects children, particularly young and school-aged, more than any other population,” said Karen Midthun, MD, director of the FDA Center for Biologics Evaluation and Research. “A vaccine containing the four virus strains most likely to spread and cause illness during the influenza season offers an additional option to aid in influenza prevention efforts.”
MedImmune is waiting for the Advisory Committee on Immunization Practices to recommend routine use of the quadrivalent intranasal vaccine before it begins manufacturing the product, said MedImmune spokesman Tor Constantino. The 15-member committee advises the Centers for Disease Control and Prevention on vaccine issues.
MedImmune’s goal is to produce the vaccine in time for the 2013-14 flu season, Constantino said. He added that manufacturing the product is not expected to take any longer than producing the trivalent immunization.
The FluMist Quadrivalent vaccine could come before ACIP as early as June, when the committee is set to meet in Atlanta.
“We’re optimistic” that a recommendation will be made for the vaccine this year, Constantino said.