"Vaccines to prevent seasonal influenza have a long and successful track record of safety and effectiveness in the United States," Dr. Karen Midthun, director of FDA's Center for Biologics Evaluation and Research, said in an agency news release.

The 2011-12 vaccine formulation is designed to protect against the three virus strains that scientists believe will be most prevalent during the coming flu season. It also includes the same virus strains used for the 2010-11 season. The 2011-12 flu vaccine protects against the same three flu strains as last year's vaccine, but a person's immunity decreases by as much as 50 percent 6 to 12 months after vaccination.  That's why it's important for children to get another flu shot this year, according to the AAP.

The group said this is only the fourth time in the past 25 years that the trivalent seasonal flu vaccine has stayed the same for two years.

The 2011-2012 seasonal influenza vaccine protects against an influenza A H3N2 virus, an influenza B virus, and the 2009 H1N1 virus that caused widespread illness in 2009-2010.

Everyone 6 months or older should receive the seasonal flu vaccine, the AAP advises. Immunization is especially important for all family members, household contacts, and out-of-home care providers of children under age 5 years and children with high risk conditions such as asthma, diabetes or nervous system disorders.

The recommendations, also advise vaccination for all women who are pregnant, considering pregnancy, or breast-feeding during the flu season.

The flu vaccine is safe for most children with a history of mild egg allergy -- that is, the egg allergy only causes hives -- but parents should consult an allergist before flu vaccine is given to children with a history of severe egg allergy, the AAP said in a journal news release. (A severe egg allergy can include trouble breathing and heart or GI problems, and epinephrine may be required to treat it).

The recommendations also include the following:

• Children 6 months through 8 years old should get two doses of the seasonal flu vaccine four weeks apart if they got none last year.
• Kids up to 8 years old need only one dose if they got at least one dose last year.
• Children 9 years and up need just one dose of flu vaccine.
• Until 6 months of age, infants are too young to be immunized. Family members are encouraged to get the flu vaccine to protect the infant.

An estimated 5 percent to 20 percent of Americans come down with the flu each year, leading to more than 200,000 hospitalizations from related complications. Flu-related deaths vary yearly, ranging from a low of about 3,000 to a high of 49,000 people, according to the U.S. Centers for Disease Control and Prevention.

There's always a chance that a flu vaccine won't be a great match against circulating virus strains. But, even if the vaccine and the circulating strains aren't an exact match, the vaccine may reduce the severity of the illness or may help prevent flu-related complications, the FDA said.

More information

To learn more about flu and flu vaccines, visit the CDC.

SOURCE: July 18, 2011, news release, U.S. Food and Drug Administration and Copyright © 2011 HealthDay.

Last Updated: November 5, 2011