SILVER SPRING, MD. — The influenza B strain in the current influenza vaccine in the United States should be replaced for the 2009-2010 influenza vaccine, according to a preliminary recommendation by a federal advisory panel, which based its decision on data on circulating viruses collected to date during this influenza season.
At a Feb. 18 meeting, the Food and Drug Administration's Vaccines and Related Biological Products Advisory Committee voted in favor of replacing the current B component of the vaccine, a B/Florida/4/2006-like virus (a B/Yamagata lineage virus), with a B/Brisbane/60/2008-like virus (a B/Victoria lineage virus).
The panelists unanimously voted to retain the two influenza A strains included in the current vaccine for the next season's vaccine. The influenza A (H1N1) strain in the current vaccine is an A/Brisbane/59/2007-like virus; the H3N2 strain is an A/Brisbane/10/2007-like virus. The panel's recommendations are not final; they will meet again to discuss the final recommendations later in the influenza season, taking into account data collected on influenza virus activity for the remainder of the season.
The panel's recommendations concur with those of the World Health Organization to retain the two influenza A strains, but to change the B strain to a B/Brisbane/60/2008-like virus, which reflects the B virus that is predominant worldwide.
On Feb. 24, the vaccine's use was endorsed for the upcoming influenza season by the Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention. The ACIP did not recommend any new age or risk groups be added to the list of those recommended to receive the vaccine, which currently includes 84% of the U.S. population. The remaining individuals—healthy adults aged 19-49 who are not close contacts of a child or other high-risk individual—are covered under the permissive recommendation for vaccination of “all individuals who want to reduce the risk of becoming ill with influenza or of transmitting it to others,” Dr. Anthony Fiore, of the CDC's influenza division, said at the ACIP meeting.
The ACIP did vote for some minor changes to its annual influenza statement, including removing the provisional “if feasible” phrase from the recommendation to vaccinate all children aged 6 months through 18 years and adding additional background information in support of vaccinating pregnant women and for routine vaccination of persons with vaccine indications during hospitalization. The ACIP also discussed the addition of information about ocular and respiratory symptoms following receipt of the injectable influenza vaccine (seen in less than 6% of recipients) to the statement's safety section, but postponed a vote on including that information until June, when more data are expected to be available.
At the FDA hearing, Alexander Klimov, Ph.D., noted that there are two major circulating lineages of influenza B viruses, Victoria and Yamagata. Worldwide, B viruses of both lineages (B/Victoria/2/87 and B/Yamagata/16/88 viruses) have cocirculated with H1N1 or H3N2 viruses, according to Dr. Klimov, chief of the virus surveillance and diagnosis branch, in the Centers for Disease Control and Prevention's influenza division. However, more than 60% of circulating B viruses are from B Victoria lineage, he said at the meeting.
During this season to date, influenza A (H1N1) viruses have predominated in the United States and in many other North American countries and in Asian countries, and the majority of the viruses have been closely related to the H1N1 strain included in the current vaccine, said Dr. Klimov, who is also deputy director of the WHO Collaborating Center for Surveillance, Epidemiology, and Control of Influenza.
Influenza A (H3N2) viruses have been cocirculating with H1N1 and B viruses in many countries, predominantly in most European countries and in Japan. Most have been antigenically similar to the H3N2 strain in the current vaccine, and have been sensitive to the influenza antivirals oseltamivir (Tamiflu) and zanamivir (Relenza), Dr. Klimov said.
In the United States, oseltamivir-resistant influenza A (H1N1) has predominated this season and has been found in 30 states, said Dr. Joseph Bresee of the epidemiology and prevention branch, in the CDC's influenza division. Oseltamivir-resistant H1N1 strains were antigenically similar or identical to the strains in the current vaccine. Viruses that have been sensitive to and those resistant to oseltamivir have been antigenically similar, he added.
This was the topic of a health advisory issued by the CDC in December, which recommended that zanamivir or a combination of oseltamivir and rimantadine (Flumadine) are more appropriate options than oseltamivir alone when influenza A (H1N1) virus infection or exposure is suspected.