A new Harris Poll confirms the findings of a recent report by the Centers for Disease Control and Prevention (CDC) that the vaccine used to prevent the flu this last winter was less effective than the flu vaccines used in previous winters.

In three previous winters people receiving flu vaccines were 33 percent, 43 percent and 24 percent less likely to get the flu than people who did not get flu shots. This year, people who received flu shots were just as likely to get the flu as those who did not get flu shots. For reasons explained below, these results probably understate the effectiveness of flu shots. However, because the surveys conducted by Harris Interactive® used identical methodologies, the difference between this winter and different years is very significant.

These data come from a Harris Poll in which 2,529 U.S. adults were surveyed online between April 7 and 15, 2008 by Harris Interactive.

One reason why the straight comparison of the incidence of flu of those who did and did not receive flu shots is not a solid measure of the vaccine's effectiveness is that those who are more likely to get the flu may also be more likely to get their flu shots. The Harris Poll suggests that this happened. Fully 72 percent of people aged 65 and over - a high risk group -- had flu shots, and 40 percent of people aged 50-64 did so. Less than 30 percent of adults under 50 did so. This could explain why people over 50 were less likely to get the flu than younger people.

Another reason why these should be treated with caution is that it is difficult for patients and physicians to make a certain diagnosis of flu, as there are other conditions that can produce similar symptoms. For all these reasons it is the trends rather than precise percentages that are important.

Other interesting findings in this survey by Harris Interactive include:

- Only 15 percent of people aged 50-64 and 65 and over reported getting the flu compared to 23 percent or more of the younger age groups;
- Although Hispanics were just as likely (36%) as the average for all Americans to get flu shots, they were much more likely to report having the flu (30%, compared to 19% for whites and 14% for African-Americans.);
- Gays, lesbians, bisexuals and transsexuals (GLBT) were as likely to get flu shots as heterosexuals, but were much more likely to report that they had the flu (33% compared to 19%);
- Only about half of the people (53%) reported having the flu visited a doctor who diagnosed flu. However, fully 78 percent of those who believe they had the flu say they are certain it was the flu;
- Thirty-eight percent of all adults think they will get a flu shot next winter. This compares with 36 percent who had flu shots for this past winter. Those planning to have flu shots include 89 percent of those who had shots last winter and only 10 percent of those who did not. Interestingly, those who had the flu are no more likely to say they will get flu shots next winter than those who did not get the flu.

A Note on the Data Released by the Centers for Disease Control (CDC)

The report of the CDC, published on April 17th, found that the flu viruses most prevalent this last winter turned out to be different than the viruses used in the vaccine. The report found that the vaccine used was somewhat effective in preventing the flu virus A (H3N2), a more virulent virus, but was completely ineffective against the Influenza B virus that circulated this past winter.

Methodology

This Harris Poll® was conducted online within the United States between April 7 and 15, 2008, among 2,529 adults (aged 18 and over) of whom 911 got a flu shot before the winter of 2007/2008. Figures for age, sex, race, education, region and household income were weighted where necessary to bring them into line with their actual proportions in the population. Propensity score weighting was also used to adjust for respondents' propensity to be online. Because the sample is based on those who agreed to participate in the Harris Interactive panel, no estimates of theoretical sampling error can be calculated. A full methodology and data tables will be made available at http://www.harrisinteractive.com.

About Harris Interactive

Harris Interactive is a global leader in custom market research. With a long and rich history in multimodal research, powered by our science and technology, we assist clients in achieving business results. Harris Interactive serves clients globally through our North American, European and Asian offices and a network of independent market research firms. To become a member of the Harris Poll Online and be invited to participate in online surveys, register at http://www.harrispollonline.com.

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