By: Jennifer C. Sarrett, PhD
The measles vaccine was developed in the mid 20th century and became widely used by the end of the 1960s. In 1971, the pharmaceutical company, Merck, combined it with the mumps and rubella vaccine to create the measles-mumps-rubella, or MMR, vaccine. In 2000, the CDC reported that measles had been eliminated (i.e., no continuous disease transmission for 12 months) and recent research reported that elimination for measles was maintained until 2011. However, each year shows increasing numbers of cases in the United States, which is the result of both historic health-care inequalities along with recent anti-vaccination movements.
Although there are many reasons parents choose not to vaccinate their children, including chronic diseases like asthma and sudden infant death syndrome, fear of Autism Spectrum Disorder (ASD) is a frequently reported concern. The CDC reports that 1 in 68 children fall somewhere on the autism spectrum, meaning they show some combination of the social-communication and behavioral features of ASD. ASD is an incredibly heterogeneous diagnosis; diagnosed individuals range from people who exhibit subtle autistic traits, such as unusual social interaction styles and strong preferences for routines, to those with more apparent manifestations, such as non-verbal communication styles and/or frequent use of repetitive behaviors for self-regulation (e.g., rocking, spinning, et cetera).
There have been two suggested links between autism and the MMR vaccine, both of which emerged in the late 1990s. The first theory suggested a link between autism and the MMR vaccine was mediated by gastrointestinal disease. British researcher, Andrew Wakefield, first proposed this theory in a 1998 article in The Lancet. This paper claimed to have discovered a new condition, autistic enterocolitis, among the twelve autistic children included in the study. These findings were largely based on parental reports that autistic symptoms began within a few weeks of the children receiving an MMR, along with the presence of various gastrointestinal symptoms. This combination of factors led Wakefield to conclude that when these children received the MMR vaccine, the vaccine virus traveled to the intestine, causing inflammation and infection. This infection allowed harmful proteins to pass through the intestinal wall, into the bloodstream, and end up in the brain, thereby causing autistic behaviors and traits.
The other perceived link between the vaccines and ASD centers on the mercury-based preservation, thimerosal, which has been used in vaccines since the 1930s. This theory states that the preservative was found in vaccines at much higher rates than recommended by the EPA. Advocates of this link suggest that thimerosal leads to neurotoxic effects, or mercury poisoning9. Although there was no evidenced-based scientific research to support this notion, in 1999 the CDC and American Academy of Pediatrics (AAP) mandated the removal of thimerosal from all vaccines as a precautionary measure.
There are several problems with this theory. First, rates of autism have continued to rise even after thimerosal was removed from vaccines. Thus, the notion that the rise in rates in the 1980s and 1990s resulted from changes in vaccines schedules is not supported. Second, thimerosal contains ethylmercury, which is different from the highly toxic methylmercury associated with mercury poisoning. A range of scientists and toxicologists has since confirmed the safety of thimerosal. Regardless, the preservative is still left out of vaccines.
Both theories of an association between vaccines and autism are based on shaky science that has not been replicated, despite multiple attempts by a variety of researchers. Studies performed around the world and using a range of approaches—from animal models to observational studies to populations studies—have explored the link between autism and vaccines and the resounding conclusion is that there is no link. Some of this research has been funded and performed by the CDC and other governmental entities. Other studies have been conducted with no links to U.S. agencies. The CDC, the AAP, the Institute of Vaccine Safety, and even Autism Speaks continue to endorse the current vaccine schedule.
Although these diseases are fairly manageable with medical intervention, they can be very dangerous. In addition to the complications listed above, measles has .03% fatality rate, meaning that 3 children will die for every 10,000 infected in the developed world (this is much higher in developing areas). Children who are not vaccinated because their parents decided against it are infecting infants who are too young to get the vaccine, children who do not have access or have conditions preventing vaccination, and older adults who did not have access to the vaccine. In other words, our most vulnerable community members are at highest risk. And much of this refusal is based on a fear of autism, which has a 0% fatality rate. This is what is, perhaps, most surprising: People have become more terrified of a developmental disability—even in the face of myriad evidence against a link between autism and vaccines—than an increased risk of a child contracting an infectious, possibly fatal, disease.
1. Perry, R. T. & Halsey, N. A. The Clinical Significance of Measles: A Review. J. Infect. Dis. 189, S4–S16 (2004).
2. Baker, J. P. The First Measles Vaccine. Pediatrics 128, 435–437 (2011).
3. Papania MJ, Wallace GS, Rota PA & et al. Elimination of endemic measles, rubella, and congenital rubella syndrome from the western hemisphere: The us experience. JAMA Pediatr. 168, 148–155 (2014).
4. Freed, G. L., Clark, S. J., Hibbs, B. F. & Santoli, J. M. Parental vaccine safety concerns: The experiences of pediatricians and family physicians. Am. J. Prev. Med. 26, 11–14 (2004).
5. Freed, G. L., Clark, S. J., Butchart, A. T., Singer, D. C. & Davis, M. M. Parental Vaccine Safety Concerns in 2009. Pediatrics 125, 654–659 (2010).
6. Developmental Disabilities Monitoring Network Surveillance Year 2010 Principal Investigators & Centers for Disease Control and Prevention (CDC). Prevalence of autism spectrum disorder among children aged 8 years - autism and developmental disabilities monitoring network, 11 sites, United States, 2010. Morb. Mortal. Wkly. Rep. Surveill. Summ. Wash. DC 2002 63, 1–21 (2014).
7. Wakefield, A. et al. RETRACTED: Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children. The Lancet 351, 637–641 (1998).
8. Offit, P. A. Autisms' False Prophets: Bad Science, Risky Medicine, and the Search for a Cure. New York: Columbia University Press (2008).
9. Wakefield’s article linking MMR vaccine and autism was fraudulent. BMJ 342, d1678–d1678 (2011).
10. Offit, P. A. Autism’s False Prophets: Bad Science, Risky Medicine, and the Search for a Cure. (Columbia University Press, 2010).
11. Wakefield, A. A statement by Dr Andrew Wakefield. The Lancet 363, 823–824 (2004).
12. Vaccine Safety & Availability - Thimerosal in Vaccines. at <http://www.fda.gov/BiologicsBloodVaccines/SafetyAvailability/VaccineSafety/UCM096228>
13. The National Vaccine Injury Compensation Program, or “vaccine court”, has awarded compensation to a few cases linking autism to vaccination. However, these cases are extremely rare and involve mediating conditions, such as a rare mitochondrial enzyme deficit[A] or encephalopathy.[B] [A] Offit, P. A. Vaccines and Autism Revisited — The Hannah Poling Case. N. Engl. J. Med. 358, 2089–2091 (2008).
[B] Largent, M. A. What If Vaccines Caused Autism? Genotopia at <http://genotopia.scienceblog.com/366/what-if-vaccines-caused-autism/>
14. Adverse Effects of Vaccines: Evidence and Causality. Institute of Medicine at <http://www.iom.edu/Reports/2011/Adverse-Effects-of-Vaccines-Evidence-and-Causality.aspx>
Dr. Jennifer C. Sarrett is currently a Visiting Assistant Professor with Emory's Center for the Study of Human Health. She studies cultural and ethical issues related to intellectual and developmental disabilities. She has also worked directly with families and children with autism as a special educator. She is also a disability and neurodiversity advocate.