The Centers for Disease Control and Prevention on Thursday recommend that all Americans over the age of 6 months get the flu vaccine to protect themselves from the virus this upcoming season.

Health officials say the strain of flu remains unchanged from the last flu season and that this year's vaccine protects against H1N1, or swine flu, and two other flu strains namely H3N2 and influenza B.

Even though the strain hasn't changed, the CDC said people who got the vaccine last year must get the flu shot again this year because the levels of protective antibodies against the viruses decreased over the course of the year.

This is especially so for the elderly and people with compromised immune systems, according to CDC.

The center estimates that 166 million doses of the vaccine will be made for this season. Last season 157 million doses were made.

Dr. Carolyn Bridges, associate director for adult immunization, Immunization Services Division in our National Center for Immunization and Respiratory Diseases, said that vaccination among health-care personnel this past season reached 63.5 percent, while it was 62 percent last season.

Pregnant women are also urged to get the vaccine because they are known to be at higher risk of severe illness from the flu.

The Morbidity and Mortality Weekly Report published Aug. 18, estimates that 49 percent of pregnant women got the vaccine for 2010 to ? 32 percent during pregnancy and 17 percent before pregnancy or after delivery.