Baby receiving a vaccination

Study demonstrates vaccines’ safety, lack of link to autism

No evidence that thimerosal-containing vaccines cause negative behaviors or result in neuropathology
October 6, 2015

New research finds no evidence that thimerosal-containing vaccines cause negative behaviors or result in neuropathology in infant primates, according to a study published recently in Proceedings of the National Academy of Sciences (PNAS).

In the study, infant animals received several pediatric vaccines containing thimerosal, a mercury-based preservative, in a schedule similar to that given to infants in the 1990s. Other animals received just the measles-mumps-rubella (MMR) vaccine, which does not contain thimerosal, or an expanded vaccine schedule similar to that recommended for U.S. infants today. Control animals received a saline injection.

Regardless of vaccination status, all animal models normal social behaviors; the administration of vaccines to infants did not result in neuropathological abnormalities or aberrant behaviors such as those often observed in autism.

Cellular analysis of the cerebellum, amygdala and hippocampus—three brain regions known to be altered in autism—was similar in vaccinated and unvaccinated animals.

“This paper is important because it takes a pretty detailed look at various types of vaccines that have been administered to infants in the past,” said Keith A. Young, Ph.D., professor in the Department of Psychiatry and Behavioral Science at the
College of Medicine at the Texas A&M Health Science Center and one of the authors of the article, “and like many previous studies, we did not find any evidence for the vaccine treatments to affect behavior or brain cell pathology.”

Laura Hewitson of The Johnson Center for Child Health and Development in Austin, Texas, a principle investigator, said the study was designed to compare the safety of different vaccination schedules, including the schedule from the 1990s, when thimerosal was used as a preservative in multi-dose vaccine preparations.

The research also involved the University of Washington’s Center on Human Development and Disability, the Infant Primate Research Laboratory at the Washington National Primate Research Center and the University of Texas Southwestern Medical Center in Dallas.

Adapted with permission from a story by the University of Washington.

— Christina Sumners

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