In May, just 49 percent described H1N1 as "very" or "somewhat" serious.
The percentage of Americans who say H1N1, also known as swine flu, is a "very serious" problem has more than doubled since May, rising from 12 percent to 28 percent.
Twenty-one percent of Americans say H1N1 is "not too serious," down from 35 percent in May. Only six percent say it is "not at all serious," down from 14 percent.
With the school year now starting up in most areas of the country, most parents say they plan to have their children vaccinated against the virus. Forty-five percent of parents with kids under 18 say they are "very likely" to have their kids vaccinated, and another 22 percent are "somewhat likely" to do so.
Another 31 percent say they are "not very" or "not at all" likely to have their children vaccinated.
Older Americans are particularly concerned about H1N1, despite some evidence that younger people may be more susceptible to the virus. Eighty-two percent of those 65 or older describe the outbreak as serious. Women are slightly more likely than men to view it as serious.
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CBSNews.com Special Report: H1N1
This poll was conducted among a random sample of 1097 adults nationwide, interviewed by telephone August 27-31, 2009. Phone numbers were dialed from random digit dial samples of both standard land-line and cell phones. The error due to sampling for results based on the entire sample could be plus or minus three percentage points. The error for subgroups is higher.
This poll release conforms to the Standards of Disclosure of the National Council on Public Polls.