copyright 2009, The Washington Post WASHINGTON -- About 40 percent of American parents have tried to get their children vaccinated against the H1N1 flu virus, but only one in three have been successful, according to a survey released Friday. High-risk adults seeking the vaccine for themselves were just as unlucky finding it. At the same time, about half of adults continue to express little interest in the vaccine now or later. The survey by the Harvard School of Public Heath sketches an American population split between people who are frustrated because they can't find the vaccine, and those who say they don't want it even when it arrives. Both groups present major challenges to public health -- one to satisfy and the other to convince. Production of vaccine against the novel H1N1 flu strain is going much more slowly than anticipated because the virus grows so slowly. As of Friday, there were 38 million doses available, which was an increase of 11 million over a week ago. Next week, about 8 million more doses will arrive, said Anne Schuchat, a physician and epidemiologist at the Centers for Disease Control and Prevention. The federal government, which is buying all the pandemic vaccine and then distributing it to state and city health departments, has ordered 250 million doses from the manufacturers. The brightest spot in the survey was the finding that 92 percent of the people who've unsuccessfully sought vaccination say they'll try again. At a press briefing Friday, Schuchat said she was heartened by that statistic. 'They weren't giving up. They recognize the value of trying to protect themselves with vaccine and sticking with it through the next several weeks,' she said. Healthy children are seeking vaccination at roughly twice the rate of chronically ill adults, even though both are among the five priority groups targeted for early vaccination. 'The proportion of parents who tried to get their kids vaccinated was larger than we anticipated,' said Robert Blendon, a professor of health policy who led the survey team. 'I think our sense was that people would start looking later in the season.' In the survey, conducted by phone on Oct. 30, 31 and Nov. 1, 41 percent of people with children under age 18 had sought vaccine for the children but only one-third of them had found it. Twenty-one percent of high-priority adults had sought it and one-third had found it. Two-thirds of the parents who weren't able to get their children vaccinated described themselves as 'frustrated.' At the other end of the spectrum, however, were adults who hadn't been vaccinated at the time the surveyors called. Sixty-two percent of them said they 'will not try' to get vaccinated later on. Of the people who said they'd tried to get information about where they might get vaccinated, 49 said they couldn't find an answer. Of the people who said the vaccine was in short supply in their communities, 67 percent doubted there'd be enough for everyone by the end of this month. The survey polled 1,073 adults age 18 and over. In theory, the sample represents the views of the entire American population within a margin of error of about 4 percentage points. 