Survey finds that flu vaccines have become slightly less effective

A Harris Poll survey conducted from April 10 to 15 revealed on Monday that although the influenza vaccine is not entirely ineffective, it has decreased in efficacy since 2004-05.

Harris Poll conducts an annual survey that records the percentage of people that receive the flu vaccine annually and compares that to how many people contract the flu. This spring, the poll surveyed 2,345 people and found 44 percent received vaccinations and 14 percent contracted the flu.

The results of the poll are similar to those of the past few winters, which ranged from 11-18 percent efficacy for 39-44 percent vaccinated population. The writers of the report said when looking at which populations received vaccinations, the conclusion can be drawn that it was effective, just not as effective as previous vaccines from the early 2000s.

For example, 73 percent of people over 65-years-old were vaccinated and seven percent contracted the flu. This does not compare, however, to the efficacy of the 2004-05 strand, which showed the lowest number of infections among those that were vaccinated.

"There are two reasons to be careful when analyzing these data," Harris Poll Chairman Humphrey Taylor said. "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."

Taylor also said those at highest risk of infection, the elderly, were most likely to receive the vaccination, which skews how the data looks at first glance.