The viruses used in making the seasonal flu vaccine are chosen each year based on information collected throughout the previous year about which flu viruses are spreading and causing the most illness. Viruses gathered by 130 influenza centers in 101 countries, as well as information on disease trends, are further analyzed by the five World Health Organization Collaborating Centers for Reference and Research on Influenza, located in Atlanta, London, Melbourne, Tokyo, and Beijing.

The seasonal flu vaccine usually protects against the three viruses that research suggests will be most common during the following season. The World Health Organization recommends the specific virus strains that will be used for vaccine production.

The committee recommended that vaccines to be used in the 2010-11 influenza season in the United States contain the following:

• A/California/7/09 (H1N1)-like virus. This is the pandemic (H1N1) 2009 influenza virus. A vaccine containing only this strain was made available to the United States in fall 2009 along with the seasonal flu vaccine.
  
• A/Perth/16/2009 (H3N2)-like virus. This is a change from the 2009-10 influenza vaccine formulation.
  
• B/Brisbane /60/2008-like virus. This is a virus that was used in the past.

Answers about the 2010-11 seasonal flu vaccine

Can people over 50 years of age get the nasal spray flu vaccine? No; a shot is recommended for this age group.

Do I need a flu vaccine this year if I got the 2009 H1N1 flu vaccine last year or this spring? Yes. The seasonal flu vaccine this year will include the 2009 H1N1 flu strain and two other strains likely to circulate. To be fully protected this flu season, you will need a vaccine to protect against all three strains. You will not have an "overdose" of 2009 H1N1 flu vaccine if you had a 2009 H1N1 flu vaccine or became ill with the 2009 H1N1 flu last year and get the seasonal flu vaccine this year. It is common for the same strain or a similar strain to be offered in the flu vaccine in successive years.

Would I have better immunity if I got the flu rather than the vaccine? A person will gain immunity against flu after getting a vaccine or, in some cases, after recovering from the flu. But complications from influenza can be more serious as we age. The risk from a vaccine is much less than the risk of getting sick with the flu. A vaccine can literally be the difference between life and death.

Can I get the flu from the flu vaccine? No. The flu vaccine cannot give you the flu. It does, however, take two weeks for the vaccine to provide full protection against the flu. Use other prevention methods such as washing your hands and staying away from those who are sick even after you have had a flu vaccine. Also, since cold and flu season occur at the same time, it is common for people to think they have the flu when really they have another illness such as a cold.

What about the high-dose vaccine? One vaccine available for the 2010-11 season is Fluzone High Dose, for people 65 and older. It contains four times the amount of antigen found in a regular shot. The extra antigen is meant to trigger a stronger immune response in older patients. Whether the improved immune response leads to greater protection against influenza is not yet known.

The Johnson County Health Department recommends you get your seasonal flu shot as soon as it is available. For local flu information, visit http://health.jocogov.org or call the flu hotline, 913-826-1263.

Source: http://answers.flu.gov/categories/941.