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APRIL 26, 2001

Good afternoon Mr. Chairman, Congressman Waxman, and members of the Committee.

I am Dr. Coleen Boyle, Acting Associate Director for Science and Public Health in the newly created National Center on Birth Defects and Developmental Disabilities at the Centers for Disease Control and Prevention (CDC). I have with me today Dr. Roger Bernier, an epidemiologist and Associate Director for Science of the National Immunization Program at CDC.

Thank you for the opportunity to testify today about autism and update you on the autism-related activities the agency has undertaken during the year since your last hearing. One major change since last year is that CDC now has established, at the direction of Congress, a new center - the National Center on Birth Defects and Developmental Disabilities. This new center, which I represent today, will increase CDC's efforts to discover causes and develop prevention and intervention strategies for birth defects and developmental disabilities. Over the next few years, CDC hopes to expand monitoring, research, and prevention activities on key birth defects and developmental disabilities and to promote the health and wellness of people with disabilities. Monitoring the prevalence of autism and conducting epidemiologic research on the causes and risk factors of autism will be among the major activities of this new center.

My field of expertise is monitoring and looking for causes of developmental disabilities, a diverse group of physical, cognitive, psychologic, sensory, and speech impairments that are usually identified between birth and age 18. Autism is one of the more serious of these developmental disabilities. It is a life-long disability characterized by impairments in social interaction and communication and a pattern of restrictive, repetitive and stereotypic behaviors, interests, and activities. The impact of autism on children and their families is tremendous. Most children with autism require long-term care and services, including special education and supervised care.

CDC's role in preventing developmental disabilities, including autism, is to determine the scope of the problem, identify preventable causes, and establish and evaluate prevention or intervention programs. There is much that is not known about autism. We do not have good data on the scope of the problem - data on the incidence rate in the United States are almost non-existent. Some studies in the1960s and 1970s found rates of 4 to 5 per 10,000 children. Studies since 1985 outside the United States reported about 12 per 10,000 children. A few recent studies, including one conducted by my program which I will mention later, found much higher rates. We do not know if these higher rates are due to different diagnostic criteria, better recognition and reporting, study phenomena, or if they represent a true increase in rates of autism.

The causes of autism remain unknown for most children. Genetics clearly plays a role in autism. Certain exposures during pregnancy are associated with autism, such as alcohol, some prescription drugs such as thalidomide, and infections such as rubella. Clearly more epidemiologic research is needed to find the causes of autism.


During the last year, CDC has engaged in a number of activities that have enhanced our understanding of the current prevalence of autism. In late April of 2000, CDC in collaboration with the Agency for Toxic Substances and Disease Registry (ATSDR) released a report of a prevalence study of autism in Brick Township, New Jersey, where local citizens were concerned that the number of children with autism in the community seemed unusually high. CDC was asked to assist in this study by the New Jersey Department of Health and Senior Services because of the complexity of trying to determine the prevalence of autism and the fact that CDC was developing the scientific methods for monitoring this disorder. The investigation found 60 children with an autism spectrum disorder (a category that includes autism and other related disorders) with 36 of these children meeting the criteria for autistic disorder, from a population of about 9,000 children. This corresponds to rates of 6.7 per 1,000 children for autism spectrum disorder and 4.0 per 1,000 children for autism. While the rate in Brick is high compared to many previous studies, there are a few very recent studies - but none in the U.S. - that have reported rates in the range reported in Brick Township.

To address the uncertainty of the finding in Brick Township as well as the lack of autism prevalence data for the U.S. in general, CDC funded in 2000, through a competitive process, four state programs in Arizona, South Carolina, Maryland/Delaware, and New Jersey to establish monitoring programs for autism. In this first year of the grant awards, CDC is working with these states to establish a common case definition and methods to identify children with autism, so that data are accurate and can be used for national projections.

In addition, CDC is completing the analysis of the first year of autism monitoring data from the CDC Metropolitan Atlanta Developmental Disabilities Surveillance Program. This program has been monitoring other serious developmental disabilities in the Metropolitan Atlanta area since 1991. Autism was added to the program in 1998 because of concern expressed by parents, educators, and clinicians about possible increases in the prevalence of this condition. A report on the prevalence of autism in 3- to 10-year-old children in greater Atlanta should be completed later this year and will be made available to the public.

Accurate prevalence data are important to understand how many children are being affected and whether that number is increasing, decreasing or constant. But those data can do even more. The database provided by a good monitoring program can be used to conduct studies of causes and risk factors for autism. In FY 2001, Congress directed CDC to establish Centers of Excellence in Autism Epidemiology. These Centers will monitor the prevalence of autism; conduct a collaborative epidemiologic case-control study to identify the causes and preventable risk factors for autism; and develop special Center projects. This year CDC will fund, through a competitive process, four such Centers. Establishing these Centers will increase the number of states that monitor the prevalence of autism and, importantly, will begin the process of collecting data for a large collaborative epidemiologic study to address possible causes of autism, including the role of environmental and genetic factors in the development of autism. The specific research objectives of the epidemiologic studies will be determined by an independent oversight committee. Representatives from autism parent advocacy groups will have an opportunity to provide input to the oversight committee during the planning phase of the epidemiologic study. CDC has successfully used this model to study the causes of birth defects and we believe that it will work equally well for autism and other developmental disabilities.


CDC has a wide range of activities to respond to questions from parents and health care professionals.

Since 1995, CDC has funded a program at Marshall University in West Virginia which provides an intensive training program and develops community support for families with young children with autism. The project addresses the needs of the family as a unit as well as the challenging behaviors of the child with autism. The program's goals are to reduce familial stress levels, to increase family access to community resources, to provide parents and educators with a positive-behavior support training program, to facilitate family support teams that help families apply knowledge gained from the training program, and to disseminate the family focus model to other states.

Another way that CDC tries to address the needs of parents is to encourage the Centers of Excellence in Autism Epidemiology to provide information to parents as one of the activities of the Center. Each center will establish a center-specific study from a list of suggested topics provided in the program announcement. Some of those topics are the development, implementation, and evaluation of intervention programs for children with autistic spectrum disorder and their families; the evaluation of economic costs; and the natural history of autism, including associated developmental disabilities and secondary conditions.

CDC has established a way for parents and others to be able to ask CDC scientists questions or express concerns about autism. We have a telephone number (770-488-7400) and a website (cdc.gov/ncbddd/dd/ddautism.htm) with information on how to contact us regarding the causes and treatments for autism and other developmental disabilities. A CDC scientist/clinician provides information about CDC-related activities on autism, addresses questions related to the causes or treatments of autism, and identifies scientists or clinicians in the community who may provide more detailed information. As the autism state monitoring programs and the Centers collect sufficient data on the prevalence and possible causes and risk factors for autism, these data will be made available in aggregate form to parents, researchers and other interested parties by a clearinghouse or network developed jointly by CDC and our state and academic partners. These data will be made available on our website as well as be published in print.


Some parents have expressed concerns about a potential link between autism and vaccines currently being used in the United States. Although the weight of scientific evidence does not support such a link, CDC is strongly committed to assuring vaccine safety. CDC is actively involved in detecting and investigating vaccine safety concerns and supporting a wide range of vaccine safety research to address safety questions. A critical part of our vaccine safety effort is the objective, scientific evaluation of safety concerns by independent experts. In collaboration with NIH and other U. S. Public Health Service agencies, CDC requested the Institute of Medicine (IOM) to conduct independent reviews by independent scientific experts to determine: 1) whether the available scientific information favors, or does not favor, vaccines playing a role in causation, 2) the level of public health priority the concern should receive, and 3) recommendations for research. As you know, the IOM issued a report this week on the possible role of MMR vaccine relative to autism. The IOM committee concluded that the evidence favors rejection of a causal relationship at the population level between MMR and autistic spectrum disorders. At its next meeting, in July 2001, the IOM will next be evaluating the role, if any, of thimerosal in developmental disorders, including autism, with a final report expected within 60-90 days of that meeting.

A second effort is to create a vaccine safety infrastructure to evaluate safety concerns. As a cornerstone of that effort, in 1990 CDC established the Vaccine Safety Datalink (VSD), a large linked database that includes all vaccinations given through the participating health plans. The VSD project allows for scientific estimation of rates of adverse events in the absence of vaccination to be compared with the rates following vaccination. This is one of the best epidemiologic tools to evaluate whether vaccines play a causal role in adverse events. CDC has expanded the VSD to enhance CDC's ability to investigate safety concerns. Three new sites have been added since last year, for a total of seven managed cared organizations that participate in the network, covering more than 2 percent of the birth cohort of the entire United States. Funding for the independent management of the VSD is awarded through a competitive process; the American Association of Health Plans currently manages the project.


The concerns raised regarding autism and vaccines have focused primarily on thimerosal, a preservative in some vaccines, and the measles, mumps, rubella (MMR) vaccine.


Despite the fact that thimerosal preservative has been effective in lowering the risk that vaccines could be contaminated by bacteria leading to serious infection, the United States Public Health Service agencies, including NIH, FDA, HRSA, and CDC, working collaboratively with the American Academy of Pediatrics and the American Academy of Family Physicians, took action in mid-1999 to begin removing thimerosal preservative from the vaccine supply. While the risk of harm from this source was only theoretical, the decision was made as a precautionary measure. The elimination of thimerosal preservative from vaccines was judged a feasible means of reducing an infant's total exposure to mercury in a world where other environmental sources of exposure may be more difficult or impossible to eliminate.

As a result of this action, all manufacturers of routinely recommended licensed pediatric vaccines are now producing for the U.S. market only vaccines that are thimerosal-free or contain trace amounts of thimerosal. The vaccines are supplied in single-dose vials which eliminates the need for a preservative.

  • The two hepatitis B vaccine manufacturers received licenses for vaccines that are either thimerosal-free or contain trace amounts of thimerosal in August 1999 and March 2000, respectively. Since June 2000, CDC has purchased only thimerosal free Hep B vaccine or Hep B vaccine with only trace amounts of thimerosal for infant immunization.
  • Since June 2000, CDC has purchased only thimerosal free Haemophilus influenzae type b (Hib) vaccines or Hib vaccine with only trace amounts of thimerosal. Historically, only 1 of 3 Hib manufacturers produced Hib vaccine with thimerosal as a preservative.
  • As of March 31, 2001, all of the Diphtheria/Tetanus/acellular Pertussis (DTaP) vaccine produced is free of thimerosal or has only trace amounts of thimerosal.

Figure 1 illustrates that the purchase of pediatric vaccines by States which contain thimerosal as a preservative, through the CDC contract, has dramatically decreased since 1998.

*FYO1 data only covers through the 2nd Quarter of FY01

Note: "No Thimerosal" category includes vaccines with no thimerosal or only trace amounts

CDC has not only supported a policy to remove thimerosal preservative from the childhood vaccine supply, it is also, along with other PHS agencies, actively investigating whether there have been any adverse effects associated with thimerosal-containing vaccines. The VSD is being used to examine the risk of neurologic disorders, including autism, associated with the use of vaccines that contain thimerosal as a preservative. In the preliminary screening phase of this investigation, no association was observed between exposure to thimerosal-containing vaccines and 12 of the 17 renal and neurologic conditions studied. A weak statistical association was observed for the other five conditions--language delays, speech delays, attention deficit hyperactivity disorder (ADHD), unspecified developmental delays, and tics. To determine whether the correlation could be seen and confirmed in an independent data base, an effort was made to collect similar data from another managed care organization. Preliminary data from that organization showed no association for speech delays, language delays or ADHD.

To further review this matter, CDC recently convened a panel of independent consultants to obtain their individual input to assist in development of a study to examine whether thimerosal-containing vaccines result in neurodevelopmental disorders in children. The consultants included experts in the fields of toxicology, neurodevelopmental psychology, speech and language, autism, pediatrics, statistics, and epidemiology, as well as a consumer representative. They provided guidance on the best research design, to address issues ranging from study site selection to which battery of standardized neuropsychological tests to administer. In addition, the consultants commented on the need for further studies on specific clinical syndromes, such as autism. CDC is presently analyzing the written comments and revising the research protocols.

MMR Vaccine

It has been suggested that vaccination, particularly with the MMR vaccine, may be related to the development of autism. At least two major hypotheses have been raised: (1) whether MMR vaccine triggers autism shortly after vaccination, and (2) whether the increase in autism diagnoses in California and elsewhere is due to the increasing use of MMR vaccine.

The suggestion that MMR vaccine triggers autism is based on some reports of cases of autism in which parents noted the onset of autistic behaviors shortly after MMR vaccination. However, scientific studies presented at last year's autism hearing and newer information argue against MMR playing a causal role. If MMR vaccine contributed to the development of autism, one would expect to see clustering of cases after MMR vaccination when a representative sample of cases with autism is evaluated. However, as discussed last year with this Committee, no such clustering was found in a review of more than 400 cases of autism by Dr. Brent Taylor, Head of the Department of Pediatrics and Child Health on the Royal Free Campus of the University College, London. The study's findings were published in the medical journal The Lancet in June 1999.

The American Academy of Pediatrics (AAP), an organization of more than 55,000 pediatricians and pediatric specialists, hosted a multi-disciplinary, international workshop on June 12-13, 2000 to review the evidence regarding a possible association between MMR vaccine, inflammatory bowel disease and autism spectrum disorders, especially autism with regression. A detailed Technical Report based on presentations at the workshop and an exhaustive review of the scientific literature will be published in Pediatrics in May 2001.

The AAP Executive Committee, in the AAP News in March 2001, stated that there is a considerable body of evidence that does not support a causal relationship between MMR vaccine and autism or inflammatory bowel disease. No data exist to suggest that separate administration of measles, mumps and rubella vaccines would offer any potential benefit over the MMR vaccine currently used in the United States. Furthermore, the Executive Committee expressed concern that such an approach would result in many underimmunized children. Therefore, the Academy continues to support fully the 2001 Immunization Schedule, which also is endorsed by CDC and the American Academy of Family Physicians.

Another of the suggestions for a possible association between MMR vaccination and autism is that the prevalence of autism diagnoses has been increasing in California, and other areas, due to increasing use of MMR vaccine. While there has been an increase in cases being diagnosed, there is scientific dispute whether this increase reflects the incidence of more autism, or better diagnosis and detection. Regardless, substantial scientific evidence does not support a role of MMR vaccine in the reported increases.

Dales, et al, recently reviewed changes over time in MMR coverage and autism diagnoses in the California Department of Developmental Services regional service center system, as published in the Journal of the American Medical Association. As shown in Figure 2, there was a 373 percent relative increase in autism case numbers between 1980 and 1994, while the MMR immunization coverage was relatively flat over the same period, increasing only 14 percent. Thus, the data were clear that MMR could not have been responsible for the increase in autism diagnoses seen in recent years.

A similar epidemiological study in the U.K., by Kaye, et al, in the British Medical Journal, also did not find an association between MMR vaccination and autism. The study used a large database of medical practices in the UK and compared diagnoses of autism over time with MMR vaccination. MMR vaccination was constant at 95 percent from 1988 to 1999. However, they found a striking sevenfold increase in the incidence rate of newly diagnosed cases of autism in this same time period.


The weight of scientific evidence does not support a causal relationship between vaccines and autism. Nevertheless, because of the continuing concerns of parents, CDC is committed to conducting research to evaluate this matter. Such research includes:

  • A study in the metropolitan Atlanta area to evaluate any association between MMR vaccination history and autism. More than 700 children aged 3-10 years old with autism were identified from CDC's Metropolitan Atlanta Developmental Disabilities Surveillance Program from the first completed year of autism monitoring by that program. The vaccination histories of these children will be compared with more than 2100 control children. A final report from this study will undergo peer review in the latter part of 2001.
  • A case-control study will be conducted in Denmark to investigate the relationship between the timing of receipt of the MMR vaccine and the risk for autism. Denmark has long-established national disease and administrative registries that can be linked via a unique personal identification number. This allows linking databases of health care, social, and educational services. Children with autism will be identified in the Danish Psychiatric Central Registry and in other databases of children with autism and other developmental problems. A comparison group will be randomly selected from the Danish Central Person Registry. Cases and controls will be linked, via their Danish personal identification number, with their vaccination records in the Public Health Insurance Registry. Also, newborn blood samples from each child can also be obtained from the Danish Biobank of Newborn Bloodspots (established in 1982 for blood samples retained after routine testing of all newborns for metabolic disorders) to test for possible biomarkers for autism apparent before onset of autistic symptoms and vaccination. Finally, supplemental risk factor data for the analyses will be obtained from the Medical Birth Register (perinatal data) and the Prevention Register (sociodemographic data). This is a 3-year study and will be completed in 2004.
  • CDC, NIH, and ten NIH-funded Centers and Programs of Excellence in autism are collaborating on a case-control study of developmental regression. Each of the ten Centers was awarded funds through the NIH competitive process. This study is planned to evaluate associations between MMR vaccination and onset of autistic regression; the study will also evaluate measles antibody levels and measles nucleic acid sequences in white blood cells of both cases and well controls.
  • CDC is collaborating with FDA on a study that follows up Vaccine Adverse Event Reporting System (VAERS) reports of autism along with a review of medical records of the cases. The VAERS contract also was awarded through a competitive process. Questionnaires will be submitted to individuals who submit reports (usually parents) of possible autism cases, and medical records will be reviewed, when available, to obtain information to classify the cases using standard diagnostic criteria to determine whether they meet the criteria for autism and, if so, the type of autism spectrum disorder.


While we must remain vigilant to assure the safety of vaccines, we must also remember that vaccines benefit the public by protecting persons from the consequences of infectious diseases. Vaccines are often cited as one of the greatest achievements of biomedical science and public health in the 20th century. We can point to the remarkable success we have had in controlling numerous infectious diseases that used to be widely prevalent in the United States, including polio, measles, and pertussis (whooping cough). In fact, several of these vaccine-preventable infectious diseases are known to cause developmental disabilities; these diseases include Haemophilus influenzae type b (Hib) and congenital rubella syndrome (CRS), one of the few known causes of autism. Rubella vaccine, by preventing CRS, is an anti-autism vaccine. Prior to routine immunization with Hib vaccine, of young children who developed Hib meningitis, 5 percent died and another 15 to 30 percent were left with residual brain damage leading to language disorders and mental retardation.

While we have made great progress in reducing the number of cases of vaccine-preventable diseases, the threats posed by vaccine-preventable diseases are known and real. The viruses and bacteria that cause vaccine-preventable diseases still circulate in the U.S. and around the world. A measles epidemic in the United States led to more than 55,000 cases of measles and more than 11,000 hospitalizations in the three years from 1989 to 1991. Additionally, pertussis has continued to be a public health threat. For example, in 1999, there were 7297 cases of pertussis in the United States, with 15 reported deaths. Continued high U.S. vaccination rates are crucial to prevent the spread of these diseases among U.S. children.


We want to assure you that CDC knows how important it is to find the causes of autism and prevent these disorders. We are committed to conducting the research that will lead to these answers. With the support of Congress, we have made a good beginning by funding autism monitoring programs in several states and the Centers of Excellence in Autism Epidemiology to look for causes of autism. We will continue to conduct research on vaccine safety. CDC efforts will continue until we have found the answers that will enable us to prevent this serious condition that affects so many American children.

Thank you, Mr. Chairman and members of the Committee, for the opportunity to testify before you today. I would be happy to answer any questions that you may have.

Last revised: May 30, 2001