Flu Shots Effective Half the Time For Winter 2004/2005, According to U.S. Poll


ROCHESTER, N.Y. -- Just over a quarter (27 percent) of U.S. adults claim to have had a flu shot before the winter of 2004/2005, when there was, initially, a shortage of available vaccine. This is a significant decline from the 35 percent who claimed to have had a flu shot for the previous winter of 2003/2004. Flu vaccines don't prevent all flus, but those who received flu shots for this winter were much less likely to get the flu (13 percent) than those who did not have flu shots (23 percent). This suggests that the vaccine was effective about half the time.

Experts on the flu say that it is easy to confuse the flu with other infections, so many people who believe that they had the flu may not have actually had it. However, a large 82 percent majority (whether or not they had received flu vaccine shots) of those who believe they had the flu say they are certain they had it; but only a third (34 percent) visited a doctor who diagnosed the flu.

These are some of the results of a nationwide Harris Poll of 2,630 U.S. adults surveyed online by Harris Interactive® between March 8 and 14, 2005.

Other interesting results of this research include:
* The differences in the prevalence of flu between those who had, and did not have, flu shots were similar for each of the last two winters (14 percent vs. 21 percent in 2003/2004 and 13 percent vs. 23 percent in 2004/2005).
* Three times as many adults tried to get flu shots but didn't get them this last winter (16 percent) as compared to the previous winter (5 percent).
* Older people are more likely to have received flu shots this last winter (2004/2005). Fully 57 percent of people aged 65 and over had flu shots compared to only 9 percent of people aged 18-24.
* About one-third of those who tried and failed to get flu shots subsequently got what they believe was the flu (5 percent out of 16 percent, of all adults).

The Harris Poll® was conducted online within the United States between March 8 and 14, 2005 among a nationwide cross-section of 2,630 adults aged 18 and over, of whom 698 got a flu shot before the winter of 2004/2005. Figures for age, sex, race, education, region and household income were weighted where necessary to bring the sample of adults into line with their actual proportions in the population. Propensity score weighting was also used to adjust for respondents' propensity to be online.

In theory, with probability samples of this size, one could say with 95 percent certainty that the results have a sampling error of plus or minus 2 percentage points. Sampling error for the various sub-sample results is higher and varies. Unfortunately, there are several other possible sources of error in all polls or surveys that are probably more serious than theoretical calculations of sampling error. They include refusals to be interviewed (non-response), question wording and question order, and weighting. It is impossible to quantify the errors that may result from these factors. This online sample is not a probability sample.

These statements conform to the principles of disclosure of the National Council on Public Polls.

About Harris Interactive
Harris Interactive Inc. is a Rochester, N.Y.-based global research company that blends premier strategic consulting with innovative and efficient methods of investigation, analysis and application. Known for the Harris Poll and for pioneering Internet-based research methods, Harris Interactive conducts proprietary and public research to help its clients achieve clear, material and enduring results.

Harris Interactive combines its intellectual capital, databases and technology to advance market leadership through U.S. offices and wholly owned subsidiaries: London-based HI Europe, Paris-based Novatris, Tokyo-based Harris Interactive Japan, through newly acquired WirthlinWorldwide, a Reston, Va.-based research and consultancy firm and through an independent global network of affiliate market research companies.

Source: Harris Interactive

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