"When there's the notion that there's something to blame, you can see where the anger would come from."
But even if the threats are emerging from a small section of those who oppose recommended vaccine schedules, those in the field say that they have a definite impact on the work they do.
"Does it stop me from speaking what I think is the truth? No," Poland said.
But, he notes, "I know of colleagues who have decided to write something slightly different or say something slightly different because they are afraid of inciting anti-vaccine groups."
Dr. William Schaffner, professor and chairman of the Department of Preventive Medicine at the Vanderbilt University School of Medicine in Nashville, Tenn., said, "The threats certainly -- as well as the anticipation of heated 'feedback' -- clearly has inhibited colleagues from engaging in the public discussion of contentious issues regarding vaccines, Lyme disease, etc."
Schaffner said he has never received such threats. But, he added, "as to myself, this unpleasantness makes me very wary; we are a society that is prone to violence."
Poland said he believes legislation should be considered to offer special protection to those in the field of vaccine research.
"Since this affects not only a person and his or her family, but indeed the public health, special provisions should be considered in terms of legal consequences," he said. "This was done, for example, in the case of abortion protesters."
But are such steps necessary? Thus far, no one has followed through with threats made against those in the field of vaccine research; likewise, there has been no report of any violence being visited on those in the autism community for their views.
Still, all involved say something should be done to help defuse the personal side of the debate.
Dr. Peter Hotez, immunologist at George Washington University in Washington, D.C., and father of a daughter with autism, said he believes that federal public health agencies, including the surgeon general's office and the National Institutes of Health, must take a more active role in dissuading the link between vaccines and autism.
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