Though measles was declared eliminated in the United States in 2000, the CDC received reports of a record number of cases last year: 644 people in 27 states.1 Currently, an ongoing outbreak that started in December at Disneyland in California has grown to at least 102 cases in 14 states.1 The amusement park is a popular destination for international travelers, including those from countries where measles is still common.
Though the United States has an excellent vaccination program, the disease can spread when “it reaches a community in the U.S. where groups of people are unvaccinated,” according to the CDC.1
The fact that most of those affected in the current outbreak are, in fact, not vaccinated1 has reignited a heated debate centered on the anti-vaccination movement led by parents who choose not to immunize their children. Driving many of these cases is a concern that the growing number of diagnoses of autism spectrum disorders (ASD) is linked to childhood vaccinations.
“The original study that started the debate was a small study2 conducted by Andrew Wakefield, MD, that reportedly found a link between the measles, mumps and rubella (MMR) vaccine, and the appearance of autism and bowel disease which was published in the Lancet in 1998,” said Guy Eslick, PhD, an associate professor of surgery and cancer epidemiology at the University of Sydney in Australia..
Though the paper was subsequently retracted after it was determined that Wakefield falsified the data, and despite the growing evidence showing no such link, the misconception persists.
“Unfortunately, for every paper that shows no relationship between vaccines and autism, there are also methodologically unsound papers that report some link between vaccines and autism. It is these unsound studies that make it more difficult for the public to distinguish fact from fiction, allowing the debate to continue,” Eslick added.
Eslick and colleagues recently conducted an analysis of methodologically-sound studies from around the world that explored the relationship between childhood vaccinations and autism.3 They included data from five cohort studies that involved 1,256,407 children, and from five case-control studies that included 9,920 children. Their findings were published in the June 2014 issue of the journal Vaccine.
“Our data did not find any increased risk associated with having childhood vaccines and the subsequent development of autism,” Eslick said, and that also pertains to specific vaccine components, such as mercury and thimerosal, which have been cited as cause for concern by some vaccination opponents.
“Thimerosal is a mercury-containing preservative that was used in vaccines to prevent contamination. Since 2001, with the exception of some influenza vaccines, thimerosal has not been used as a preservative in routinely recommended childhood vaccines,” said Frank DeStefano, MD, MPH, FACPM, director of the Immunization Safety Office at the CDC in Atlanta.
In addition to the decreased use of thimerosal, numerous studies investigating the relationship between thimerosol and autism have found no connection. “Hundreds of thousands of children who received thimerosal-containing vaccines were compared to hundreds of thousands of children who received the same vaccines free of thimerosal. The results show that without a doubt, autism is not caused by thimerosal in vaccines.”
A 2013 CDC study that DeStefano co-authored is one of many showing that there is no causal link between vaccines and autism.4 Comparing data from 256 children with autism to data from 752 children without autism, the researchers examined the number of antigens from vaccines received during the first two years of life. Antigens are substances that cause the immune system to produce disease-fighting antibodies. The results show that the total number of antigens from vaccines was the same for both groups of children.
The findings also demonstrate that the number of vaccine antigens has declined in recent years because of changes in vaccines. For example, the older pertussis vaccine prompts the production of about 3,000 antibodies, while the newer version causes the production of six or fewer antibodies.
“The evidence is clear: vaccines do not cause autism,” said DeStefano. Autism advocacy organizations like Autism Speaks5 and the Autism Science Foundation6 support that conclusion and encourage parents to have their children vaccinated.
Clinicians can reassure patients that vaccines are safe and effective. The U.S. has a safety system that rigorously tests vaccines before they receive FDA approval and continuously monitors them after they become available to the public.
“Clinicians are patients’ most trusted source of information about vaccines, and should be prepared to answer questions about vaccine safety. Vaccines are our best defense against many serious, preventable diseases, and clinicians can help ensure that patients get recommended, live-saving vaccines,” said DeStefano.
Tori Rodriguez, MA, LPC, is a psychotherapist and freelance writer based in Atlanta.
- Centers for Disease Control and Prevention. Measles Cases and Outbreaks. Page updated February 2, 2015 http://www.cdc.gov/measles/cases-outbreaks.html
- Wakefield AJ, Murch SH, Anthony A. RETRACTED: Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children. Lancet. 1998; 351(9103):637-41.
- Taylor LE, Swerdfeger AL, Eslick GD. Vaccines are not associated with autism: An evidence-based meta-analysis of case-control and cohort studies. Vaccine; 2014; 32(29):3623-9.
- DeStefano F, Price CS, Weintraub ES. Increasing Exposure to Antibody-Stimulating Proteins and Polysaccharides in Vaccines Is Not Associated with Risk of Autism. Journal of Pediatrics; 2013; 163(2):561-7.
- Autism Speaks: http://www.autismspeaks.org/science/policy-statements/information-about-vaccines-and-autism
- Autism Science Foundation: http://www.autismsciencefoundation.org/autismandvaccines.html
This article originally appeared on Psychiatry Advisor