WASHINGTON (Reuters) - Congressional Democrats on Wednesday introduced legislation that would repeal a law that gives vaccine, drug and medical device makers broad protection against lawsuits in a public health or bioterror emergency. Democrats generally agree there should be some legal protections for certain vaccines but say the Republican version defined health emergency too broadly and did not compensate people who were injured. The liability provision, strongly favored by Senate Majority Leader Bill Frist of Tennessee, was added to a defense bill enacted in December. Democrats would have an uphill struggle trying to repeal it.