Vaccines and autism: Science, politics, and the media

What is science?  Science is the systematic enterprise of gathering knowledge about the world and organizing and condensing that knowledge into testable laws and theories Wilson, Edmund O. in Consilience

What is science?  Formulate a hypothesis and establish burdens of proof. Proofs are subjected to statistical analysis. u Science includes rigorous controls that allows one to isolate the effects of one variable.

Two Foundations of Science  Scientific data should be subjected to peer- review (published in good journals) u Scientific data should be confirmed by other investigators (data must be reproducible) Park, R. Voodoo Science: the road from foolishness to fraud (Oxford University Press, 2000)

Autism and vaccines A major cause of the Roman empire’s decline…was its replacement of stone aqueducts by lead pipes…Roman engineers, the best in the world, turned their fellow citizens into neurologic cripples. Today our own “best and brightest” with the best of intentions, achieve the same end through childhood vaccination programs yielding the modern scourges of hyperactivity, learning disabilities, autism, appetite disorders, and impulsive violence. Coulter, Harris, PhD, 1982

Wakefield, A.J., et al. Lancet 351: , 1998.

The “Wakefield” study  Theory: The MMR vaccine induces a series of events that includes intestinal inflammation, loss of intestinal barrier function, entrance into the bloodstream of encephalopathic proteins, and subsequent development of autism. u Study design: 12 children (8 with autism) in the United Kingdom who recently received the MMR vaccine.

The “Wakefield” study Findings in support of theory u Symptoms of autism first noted by parents within 1 month of receiving the MMR vaccine in all eight children. u Seven of eight children with autism had non-specific colitis and “reactive ileal and colonic hyperplasia” associated with GI symptoms.

The “Wakefield” study Findings at variance with hypothesis u Cannot assign causal link between receipt of vaccine and onset of autism given absence of control group.

Determining causality DiseaseNo disease Vaccine a b No vaccine c d Risk in “vaccine” group = a /a + b Risk in “no vaccine” group c/ c + d

The Power of Box A u “Popular induction depends upon the emotional interest of the instances, not on their number.” (Bertrand Russell, 1927) u Daniel Kahneman and the science of uncertainty: “Judgment Under Uncertainty: Heuristics and Biases.” u Rotavirus vaccine and intussusception at the ACIP.

 Extraordinary claims should be backed up by extraordinary evidence Sagan, Carl

Consequence of MMR fears  Between 1989 and 1991, about 70% of children in US were immunized with measles vaccine. u As a consequence, 55,000 cases of measles resulted in 11,000 hospital admissions and 123 deaths. u Recent outbreaks of measles in England and Ireland.

The “Denmark” study  Retrospective cohort study of all children born in Denmark between 1991 and u Cohort included 537,303 children. 444,655 (82%) children had received the MMR vaccine. Madsen KM, et al. A population-based study of measles, mumps, and rubella vaccination and autism. N Engl J Med 2002;347:

The “Denmark” study  RR for vaccinated as compared with unvaccinated children for development of autism was 0.92 (95% CI, ) and for ASD was 0.83 (95% CI, ). u No association between the age at the time of vaccination or the time since vaccination, and the development of autism.

Science and the media  “ We cannot rule out the possibility that, in certain isolated, rare instances, the vaccine might have caused a rare case of autism,” said Dr. Hershel Jick of Boston University Medical Center. “But it is certainly not the major villain.” Los Angeles Times, March, 2001

Science and politics  “ You (the IOM) put out a report to the people of this country saying that it (the MMR vaccine) doesn’t cause autism and then you’ve got an out in the back of the thing. You can’t tell me under oath that there is no causal link, because you just don’t know, do you?” Dan Burton (R-Ind), April 25 th, 2001

Science and the media 60 Minutes: “The MMR Vaccine” Host: Ed Bradley Producer: Trevor Nelson Date Aired: November 12, 2000

Lessons for the media u Understand the basic tenets of science. Studies that have not been both peer- reviewed and reproduced should be interpreted with caution. u Difference between balance and perspective. u “First, do no harm.”

Lessons for parents  Understand the basic principles of science. Reasonable to be skeptical of scientists (or those representing themselves as scientists), but not reasonable to be skeptical of the scientific method.

vaccine.chop.edu Vaccine Education Center at The Children’s Hospital of Philadelphia ® Facts About Childhood Vaccines