The results of the survey, released Friday by the Harvard School of Public Health, shows that only about one-fifth of Americans had a vaccination against swine flu by the end of January, The New York Times reported.
Robert Blendon, director of opinion research at Harvard's School of Public Health, told the newspaper that "a steady core of adults" has resisted all warnings and appeals from public health officials about the swine flu.
He said the survey showed that only about 40 percent of teens and children had been vaccinated even though the swine flu hits them the hardest. The poll also found that most parents who didn't get shots said they believed the threat had passed, while others expressed fear of the vaccine.
"But that could all change overnight if we get a third wave in late February -- and we still could," Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, told the Times.
The poll surveyed 1,419 adults, including 377 parents, and carried a margin of error of 3 percentage points.
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