Prevalence of Flu and Use of Flu Shots Last Winter Fairly Typical of Last Decade

NEW YORK, May 14, 2013 /PRNewswire/ -- Last winter's flu season was fairly typical of other winters over the last decade, with the prevalence of the flu and the number of people who had flu shots both fairly close to the averages for that time period.  The effectiveness of flu vaccines also seems to have been fairly typical. 

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These are some of the findings of a new Harris Poll® survey of 2,345 U.S. adults, surveyed online between April 10 and 15, 2013 by Harris Interactive.  (Full findings and data tables available here)

Some of the main findings of this Harris Poll are:

• 44% of all adults report that they had flu shots. This compares with 40%, 39%, 44% and 40% over the four previous winters.
• 14% of adults believe that they had the flu last winter, compared to 18%, 12%, 11% and 11% over the four previous winters.
• As in most of the Harris Polls on this topic over the last nine years, the numbers of people who believe they had the flu was almost the same for people who had flu shots (14%) and those who did not (15%).  However, it would be a mistake to conclude from this that the vaccine was ineffective. There is clear evidence in this poll that people who were more vulnerable were also more likely to have received shots (see below).
•  There seems to be have been wide variations in the effectiveness of the flu vaccines used in different years , based on the numbers of people who were and were not vaccinated who think they got the flu.  The vaccines seem to have been most effective in the winters of 2003-2004 and 2004-2005, and much less effective in the winter of 2010-2011.
• Because flu symptoms are sometimes confused with symptoms of other conditions, people who said they had had the flu were asked if they had visited a doctor who had diagnosed flu.  Only 35% of those had flu shots and who also believe that they had the flu report that their flu was diagnosed by a doctor, a big drop from the number in the two previous winters (55% and 60%).
• Efforts to vaccinate the elderly, who are more vulnerable, seem to have been quite effective. Fully 73% of people aged 65 and over were vaccinated, and only 7% report that they had the flu.  People aged 18-24 were the least likely (22%)  to be have had flu shots, and people aged 30-39 were the most likely (21%) to believe that they had the flu.
• White adults were much more likely to have had flu shots than African-Americans and Hispanics (50% compared to 39% and 23%). Hispanics were much more likely to believe they had the flu than whites or African-Americans (22% compared to 13% and 15%).

Reasons for caution
This is a complicated subject and there are several reasons for caution in interpreting these findings – for example, it would be erroneous to conclude that the flu vaccines used last winter had no effect.  However, it is probably safe to conclude that the flu vaccines used to protect people over the last four winters were less effective than the vaccines used to protect people in the winters of 2006-07, 2004-05, and 2003-04.  In each of those winters, people who received shots were significantly less likely (especially in 2004-05) to get the flu (or to believe they got it) than were those who did not have flu shots.

"There are two reasons to be careful when analyzing these data," explains Harris Poll Chairman Humphrey Taylor.  "One is that the diagnosis, and particularly self-diagnosis, of the flu is not very reliable.  Other infections can produce flu-like symptoms.  This raises the question of whether some people who report having had flu shots and then having the flu may have been mistaken."  This year's survey, similar to last year's survey, finds that about three fifths of these people are "certain" they had the flu (61%) and spent one or more days in bed (62%).  However, just over one-third (35%) visited a doctor who diagnosed the flu – far fewer than in most previous years.

"Furthermore," continues Taylor, "the absence of a direct correlation between those who had flu shots and those who did not get the flu does not mean that the flu shots had no effect, because those who are more likely to get the flu may also be more likely to get flu shots."  The Harris Poll suggests that this happened.  Fully 73% of people aged 65 and over – a high risk group – had flu shots, and 51% of people aged 50-64 did so.  Far fewer adults under 50 were vaccinated.  The particularly high incidence of flu shots among those 65 and older could explain why this group was less likely to get the flu than younger people.

To view the full findings, or to see other recent Harris Polls, please visit the Harris Poll News Room.

Methodology
This Harris Poll was conducted online within the United States between April 10 and 15, 2013 among 2,345 adults (aged 18 and over). Figures for age, sex, race/ethnicity, education, region and household income were weighted where necessary to bring them into line with their actual proportions in the population. Where appropriate, these data were also weighted to reflect the composition of the adult online population. Propensity score weighting was also used to adjust for respondents' propensity to be online.

All sample surveys and polls, whether or not they use probability sampling, are subject to multiple sources of error which are most often not possible to quantify or estimate, including sampling error, coverage error, error associated with nonresponse, error associated with question wording and response options, and post-survey weighting and adjustments. Therefore, Harris Interactive avoids the words "margin of error" as they are misleading. All that can be calculated are different possible sampling errors with different probabilities for pure, unweighted, random samples with 100% response rates. These are only theoretical because no published polls come close to this ideal.

Respondents for this survey were selected from among those who have agreed to participate in Harris Interactive surveys. The data have been weighted to reflect the composition of the adult population. 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.

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

The results of this Harris Poll may not be used in advertising, marketing or promotion without the prior written permission of Harris Interactive.

The Harris Poll^® #26, May 14, 2013
By Humphrey Taylor, Chairman, The Harris Poll, Harris Interactive

About Harris Interactive
Harris Interactive is one of the world's leading market research firms, leveraging research, technology, and business acumen to transform relevant insight into actionable foresight. Known widely for the Harris Poll® and for pioneering innovative research methodologies, Harris offers proprietary solutions in the areas of market and customer insight, corporate brand and reputation strategy, and marketing, advertising, public relations and communications research. Harris possesses expertise in a wide range of industries including health care, technology, public affairs, energy, telecommunications, financial services, insurance, media, retail, restaurant, and consumer package goods. Additionally, Harris has a portfolio of multi-client offerings that complement our custom solutions while maximizing our client's research investment. Serving clients in more than 196 countries and territories through our North American and European offices, Harris specializes in delivering research solutions that help us - and our clients—stay ahead of what's next. For more information, please visit www.harrisinteractive.com.

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SOURCE The Harris Poll