Selecting Viruses for the Seasonal Influenza Vaccine
The seasonal influenza vaccine is designed to protect against the influenza viruses research indicates are most likely to spread and cause illness among people during the upcoming flu season. Flu viruses are constantly changing, so the vaccine is updated each year based on which influenza viruses are making people sick, how those viruses are spreading, and how well the previous season’s vaccine protects against those viruses.
More than 100 national influenza centers in over 100 countries conduct year-round surveillance for influenza. This involves receiving and testing thousands of influenza virus samples from patients with suspected flu illness. The laboratories send representative viruses to five World Health Organization (WHO) Collaborating Centers for Reference and Research on Influenza, which are located in the following places:
- Atlanta, Georgia, USA (Centers for Disease Control and Prevention, CDC);
- London, United Kingdom (National Institute for Medical Research);
- Melbourne, Australia (Victoria Infectious Diseases Reference Laboratory);
- Tokyo, Japan (National Institute for Infectious Diseases); and
- Beijing, China (National Institute for Viral Disease Control and Prevention).
In February of each year, WHO consults with experts from WHO Collaborating Centers, Essential Regulatory Laboratories, and other partners to review data generated by the worldwide network of influenza laboratories. Afterward, WHO makes recommendations for the composition of the seasonal influenza vaccine for the Northern Hemisphere.
The U.S. Vaccines and Related Biological Products Advisory Committee (VRBPAC) - which is a part of the U.S. Food and Drug Administration (FDA) – considers the WHO recommendations and makes a final decision regarding composition of seasonal flu vaccine for the United States.
The WHO Vaccine Composition Meeting was held on February 21, 2013, at WHO headquarters in Geneva, Switzerland.
On February 27, 2013, VRBAC met and approved for the United States the following WHO-recommended composition for the Northern Hemisphere 2013-2014 influenza vaccine:
- an A/California/7/2009 (H1N1)pdm09-like virus;
- an A(H3N2) virus antigenically like the cell-propagated prototype virus A/Victoria/361/2011;
- a B/Massachusetts/2/2012-like (B/Yamagata lineage) virus.
Compared to the 2012-2013 seasonal influenza vaccine, the H1N1 component is the same, the H3N2 component is the same*, and the B component is different.
This season, most seasonal influenza vaccines will have the above-listed three virus components, but some quadrivalent (four-component vaccine) will also be available. Quadrivalent vaccine this year includes the three viruses listed in the bullets above, and also a B/Brisbane/60/2008-like (B/Victoria lineage) virus.
The WHO Vaccine Composition Meeting for Southern Hemisphere 2014 influenza season vaccines was held September 23-26, 2013, at WHO headquarters in Geneva, Switzerland. The recommended composition is the same as the composition of 2013-2014 Northern Hemisphere vaccines.