On July 24, 鶹ý published a blog post on Robert F. Kennedy Jr.'s upcoming book attacking thimerosal in vaccines. Kennedy responded in an interview Tuesday; his comments are included in italics below in an abbreviated version of the original post.
Robert F. Kennedy Jr. is putting out a book on the dangers of thimerosal in vaccines, raising an issue that many in the medical and scientific communities hoped was long settled.
The book, "," is scheduled to be available on Aug. 4.
Kennedy said in an interview that publishing the book was a last resort. "We wanted to go to the CDC and HHS [the Department of Health and Human Services], show them the science, and ask them to quietly remove thimerosal from vaccines," he told 鶹ý. But once he did meet with people from those agencies, "they made it clear they were not going to make the changes ... so we went ahead and published it."
Vaccine Advocates Respond
After a -- which he has been working on for more than a decade -- came out in The Washington Post Magazine, a rebuttal of sorts appeared in the website Slate, entitled "" In it, the author writes, "The number of measles cases in the U.S. tripled last year -- an entirely preventable disease whose resurgence has been made possible in part by Kennedy's tireless efforts. There are a lot of people who deserve your sympathy as they work tirelessly and thanklessly to improve the world. Robert F. Kennedy Jr. is not one of them."
Kennedy said that he is not the reason that some parents are refusing to vaccinate their children. "The people reducing vaccine coverage are those putting unnecessary neurotoxin into our vaccines. Vaccine coverage is reduced because people don't trust vaccine regulators. They don't trust that they are telling them the truth."
Vaccine advocates were quick to dismiss Kennedy's claim that thimerosal can cause neurodevelopmental problems. "This hypothesis ... about thimerosal was raised 15 years ago and answered 5 years ago -- it's done," , director of the Vaccine Education Center at the University of Pennsylvania in Philadelphia, said in a phone interview.
But Kennedy disputes that idea, noting that a team of researchers he worked with spent 2 1/2 years scouring the medical literature for every peer-reviewed study ever done on thimerosal safety. "They found 500 peer-reviewed studies that had 1,400 references that addressed directly the issue of thimerosal safety, and there was no single publication that said thimerosal was safe."
He added that five studies -- done under the auspices of either the CDC or the vaccine industry -- were epidemiological studies that did not find a signal for neurotoxicity. However, "those studies had big holes in them," he said.
Offit disagreed. "It doesn't matter what Bobby Kennedy Jr. does -- the only thing is what the data show," he said. "The question is, are the levels [of mercury] contained in vaccines shown to be harmful? And the answer is no. Thimerosal is ethyl mercury, not environmental mercury, and it's excreted from the body far more quickly ... Breast milk contains far higher [mercury] levels than you would ever get from vaccines."
Vaccines are a victim of their own success, Offit noted. ""People don't fear [vaccine-preventable] diseases because they don't see them."
He also said he understands why parents push back against vaccination. "We ask parents to get their children vaccines to prevent 14 different diseases; they can get as many as five [shots] at one time. I understand the pushback." But now that there have been more outbreaks of vaccine-preventable diseases, "we're starting to see parents push back [the other way]. You don't hear the anti-vaccine people so much any more."
, professor of preventive medicine and infectious diseases at Vanderbilt University in Nashville, Tenn., told 鶹ý that it's very difficult to change the minds of "true believers" like Kennedy.
Psychological data show that "if people have very firm beliefs on a subject -- a subject close to their heart in which they have emotional involvement -- when they're presented data contrary to that belief, they double down," said Schaffner, who is also past president of the National Foundation for Infectious Diseases. "They become even more firmly convinced their original concept is correct."
Kennedy, for his part, said he is willing to be persuaded otherwise. "This isn't an issue I want to be involved in," he said. "I just want somebody to read the science and tell me where I got it wrong. I would love to see a credible study ... because I could drop this issue and apologize to CDC and HHS and walk away."
Pay and Practice is a blog for readers with an interest in health policy.