Far Fewer People Had Flu in Winter of 2009/2010 Than in Previous Years
Only 12% of adults think they had the flu this past winter, fewer than the 15% to 21% who thought they had the flu in other winters since 2004. We emphasize “think” because it is widely believed that not everyone who has flu-like symptoms actually has the flu.
However, there is no evidence that flu shots should get the credit for the decline in the number of people with the flu. The 39% of adults who had flu shots is almost the same as those who had them in two previous winters (40% in 2008-2009, and 36% in 2007-2008). Furthermore, for the third year running – the proportion of adults who believe they got the flu was the same (12%) among those who did and did not get flu shot.
These are some of the findings of a new Harris Poll® survey of 2,755 U.S. adults, surveyed online between April 12 and 19, 2010 by Harris Interactive.
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 three 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.
Reasons for Caution
There are two reasons to be careful when analyzing these data.
| 1) | 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 previous years, finds that about three-quarters of these people are “certain” they had the flu (72%) and spent one or more days in bed (76%). However, only just two in five (39%) visited a doctor who diagnosed the flu. | |
| 2) | Furthermore, the absence of a correlation does not necessarily 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 68% of people aged 65 and over – a high risk group – had flu shots, and 46% of people aged 50-64 did so. Far fewer adults under 50 did, which could explain why people over 50 were less likely to get the flu than younger people. |
Other findings of this Harris Poll include:
- Men and women were equally likely to have had flu shots (38% for men, 39% for women) and equally likely to believe they had the flu (12% for both men and women).
- People under 40 were more likely than people over 40 to report having had the flu. This may be a result of the higher incidence of flu shots among older people or the higher levels of immunity built up over time by older people.
- African-Americans (6%) are much less likely than Whites (12%) and Hispanics (19%) to report having had the flu, although similar proportions of these three groups received flu shots.
- Most (66%) of those who report having had the flu this winter believe they had a “regular flu.” Only 13% believe they had the H1N1 flu virus. More than a fifth (22%) were not sure.
- The proportion of adults who think they will have a flu shot next winter is the same as those who had one this last winter (39%), and they are mostly the same people. Only 3% of those who had a flu shot say they will not get one for this coming winter.
