In the first such study to estimate the effectiveness of side airbag protection, the IIHS found side airbags that protect the chest and abdomen, but not the head, also are reducing deaths but are less effective -- about 10 percent.
Each year more than 9,000 passenger vehicle occupants die in side impacts and head injuries are a leading cause, the IIHS said.
"The need for head protection in side impacts has been obvious for some time," Brian O'Neill, IIHS president said in a statement.
"Before head-protecting airbags were available there was virtually nothing to prevent people's heads from being struck by intruding vehicles or rigid objects like trees and poles in serious side impact crashes."
2014: The Year in Music [PHOTOS]