CDC: Seasonal Vaccine No Help Against Swine Flu

U.S. health officials say they are "very pessimistic" that the seasonal flu vaccine protects against the unique swine flu infecting people in the United States, Mexico and other countries.

A U.S. Centers for Disease Control and Prevention official said Sunday afternoon that tests of the seasonal vaccine and the new virus show no cross-reaction, suggesting that people who got the vaccine have no added protection against the new bug.

It's possible that people who have been exposed to flu viruses every year — especially older people, with a greater exposure history — may have some natural immunity, the CDC official said in a call with reporters.