Michigan ? The first head-to-head comparison of the flu shot and the new FluMist inhalable vaccine found shots surprisingly more effective in adults.

The study, involving about 1,250 Michigan adults, found that a needle in the arm was 67 percent to 77 percent successful at preventing the flu, depending on the measurement method. The nasal spray was 30 percent to 57 percent effective.

Flu shots contain killed flu viruses. FluMist, approved in 2003, delivers weakened live viruses.

“This study suggests that maybe it doesn’t really offer any specific benefit beyond what you would get from just a regular flu shot, and under certain circumstances, it may not be quite as good,” said Dr. John Treanor, a vaccine expert at the University of Rochester Medical Center.

FluMist was designed with children in mind, and an unpublished study sponsored by the company suggested it was more effective in youngsters than a shot in the arm, as measured by the children’s immune-system responses.