Flu shot's effectiveness questioned

As Americans line up for flu shots, they should consider that the vaccines may be far less effective than thought, according to a new study.

Michael Osterholm, an infectious disease specialist at the University of Minnesota, and his colleagues found in a study that the most common flu vaccine in the United States is effective for 59 percent of healthy adults, well below the 70 percent to 90 percent level previously reported.

"We're stuck with a vaccine that has been around for 60 years and not changed much," Osterholm said.

He stressed the need for a new generation of flu shots, particularly in the face of a future pandemic and added that there is a lack of information about how well the vaccine works in children and in adults older than 65. Both groups are most at risk from flu-related illness or death.

U.S. health officials recommend that all Americans older than 6 months get a flu shot.

In a study published in The Lancet Infectious Diseases journal, Osterholm and colleagues analyzed 31 vaccine studies published in the last 40 years.

The studies tested for the presence of flu in laboratory tests rather than counting an increase in flu antibodies -- a faster method but one that researchers say tends to overestimate the vaccine's efficacy.

A meta-analysis of the 31 studies also showed that a newer type of vaccine that uses a live virus was 83 percent effective in protecting children between 6 months and 7 years old.

But this type of vaccine is not recommended as the best treatment for children by the CDC group that decides immunization practices in the United States, the study's authors said. -- Reuters