Questions & Answers

Vaccine Selection for the 2010–2011 Influenza Season

How are the viruses selected to make flu vaccine?

The viruses used in making seasonal flu vaccines are chosen each year based on information collected over the previous year about which flu viruses are spreading and causing the most illness. Viruses gathered by 130 national influenza centers in 101 countries as well as information on disease trends are further analyzed by the five World Health Organization (WHO) Collaborating Centers for Reference and Research on Influenza located in Atlanta, USA (Centers for Disease Control and Prevention, CDC) ; London, United Kingdom; Melbourne, Australia; Tokyo, Japan; and Beijing, China. While there are many different flu viruses, the seasonal flu vaccine is usually a trivalent vaccine (a three component vaccine) that protects against the three viruses that research suggests will be most common during the following season and WHO recommends specific virus strains that can be used for vaccine production. The 2009 H1N1 vaccine that was made to protect against the pandemic virus first detected in April was a monovalent (one-component) vaccine, that only protected against the 2009 H1N1 viruses.

When and where will the group meet to determine the vaccine composition for the 2010-2011 seasonal influenza vaccine?

The selection process of which influenza viruses will be used in the Northern Hemisphere 2010-2011 seasonal influenza vaccine is currently underway. Preliminary teleconferences to discuss surveillance data were held on January 14 and February 4, 2010. The final WHO Vaccine Composition Meeting will be held February 14-19, 2010 at the WHO headquarters in Geneva, Switzerland.

Who is included in the group that will make the vaccine virus selections?

The group changes from year to year, but is comprised of WHO representatives from the WHO Collaborating Centers, Essential Regulatory Labs, and others from the Global Influenza Surveillance Network (GISN). After WHO makes its recommendations for the Northern Hemisphere, the FDA Vaccines and Related Biological Products Advisory Committee (VRBPAC) meets in Bethesda, Maryland on February 22, 2010 to concur with or modify WHO's recommendation for the United States.

How many flu viruses will be included in the seasonal vaccine for 2010-2011?

In past years, seasonal influenza vaccines have contained three influenza viruses, which are chosen based on information about recently circulating seasonal viruses. The composition of the 2010-2011 seasonal influenza vaccine will likely be trivalent (with three different vaccine viruses), although committee members may consider other options. The Southern Hemisphere's 2010-2011 vaccine includes the following three vaccine viruses: an A/California/7/2009 (H1N1)-like virus, an A/Perth/16/2009 (H3N2)-like virus and a B/Brisbane/60/2008-like virus. The H1 strain included in this vaccine is the same as the one used in the pandemic 2009 H1N1 vaccine.

When will the vaccine viruses selected for the 2010-2011 seasonal influenza vaccine be announced?

After FDA (VRBPAC) meets in February to review WHO's recommendations as they relate to the U.S., WHO and FDA will post the recommendations for the composition of the U.S. seasonal influenza vaccine on their websites. This information will also be available on CDC's website.