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(Austin, Texas) – September 28, 2015 - New research finds no evidence that thimerosal- containing vaccines cause negative behaviors or result in neuropathology in infant primates, according to a study that will be published today in the Proceedings of the National Academy of Sciences. In this study, conducted by Dr. Dwight German of the University of Texas Southwestern School of Medicine, and colleagues, infant rhesus macaques 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 US infants today. Control animals received a saline injection.
Regardless of vaccination status, all animals developed normal social behaviors. Cellular analysis of three brain regions, the cerebellum, amygdala and hippocampus (all known to be altered in autism), was similar in vaccinated and unvaccinated animals.
“This comprehensive analysis of social behavior and neuropathology in 12-18 month old rhesus macaques indicated that vaccinated primates were not negatively affected by thimerosal; the same was true for animals receiving an expanded 2008 vaccine schedule, which is similar to that recommended for US infants today” explained Dr. Laura Hewitson of The Johnson Center for Child Health and Development, one of the principle investigators working on the study. Hewitson was part of a team of researchers from The Johnson Center; the University of Texas Southwestern; the Center on Human Development and Disability Infant Primate Research Laboratory; the Washington National Primate Research Center (WaNPRC) at the University of Washington, Seattle WA; and Texas A&M Health Science Center & Central Texas Veterans Health Care System.
According to Hewitson, 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 data from this study indicate that administration of TCVs and/or the MMR vaccine to rhesus macaques did not result in neuropathological abnormalities,or aberrant behaviors, like those often observed in autism.

Citation
Administration of thimerosal-containing vaccines to infant rhesus macaques does not result in autism-like behavior or neuropathology. Bharathi S. Gadad, Wenhao Li, Umar Yazdani, Stephen Grady, Trevor Johnson, Jacob Hammond, Howard Gunn, Britni Curtis, Chris English, Vernon Yutuc, Clayton Ferrier, Gene P. Sackett, C. Nathan Marti, Keith Young, Laura Hewitson and Dwight C. German. PNAS
This article can be downloaded for free here.
This study was supported by The Ted Lindsay Foundation, SafeMinds, National Autism Association, and the Johnson and Vernick families. This work was also supported by WaNPRC Core Grant RR00166 and CHDD Core Grant HD02274.
About The Johnson Center
The mission of The Johnson Center for Child Health and Development is to advance the understanding of childhood development through clinical care, research, and education.
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For Immediate Release
Contact: .(JavaScript must be enabled to view this email address)
512-732-8400
(Austin, Texas) – February 18, 2015 - A research study published today in Environmental Health Perspectives reported that vaccination of infant macaques with thimerosal-containing vaccines did not negatively impact neurodevelopment, cognition, or behavior. In this study 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 US infants today. Control animals received a saline injection. Regardless of vaccination status, all animals developed normally.
“This comprehensive study of infant primate development, including analyses of learning, cognition, and social development, indicated that vaccinated primates were not negatively affected by thimerosal or the MMR vaccine; the same was true for animals receiving an expanded vaccine schedule” explained Dr. Laura Hewitson of The Johnson Center for Child Health and Development, the principle investigator of the study.
Hewitson worked with a team of researchers at the Center on Human Development and Disability Infant Primate Research Laboratory and the Washington National Primate Research Center (WaNPRC) at the University of Washington, Seattle WA. According to Hewitson, the study was designed to compare the safety of different vaccination schedules, including the schedule from the 1990s, when thimerosal was still used as a preservative in multi-dose vaccine preparations. Although in 1999 the FDA and the American Academy of Pediatrics recommended that thimerosal be removed from vaccines in the US, it is still used as a preservative in multi-dose flu shots, which are recommended for pregnant women and children 6 months of age and older.
“This is the first time the safety of the entire pediatric vaccine schedule has been investigated in a relevant animal model,” said Dr. Judy Van de Water from the UC-Davis MIND Institute, who was not involved in this study.
Hewitson also noted, “As with any animal study, assessments were implemented under controlled laboratory conditions. We did not test all of the interacting variables that could contribute to an adverse outcome, such as birth weight, gestational age, genetic vulnerability, or in utero and post-natal chemical exposures. The interaction between multiple environmental exposures or genetic factors that may impact vaccine response, which is an important aspect of the vaccine debate, was not addressed in this study. Despite these limitations, the data in this primate study overwhelmingly provides support for the safety of pediatric vaccines.”
Citation
Examination of the Safety of Pediatric Vaccine Schedules in a Non-Human Primate Model: Assessments of Neurodevelopment, Learning, and Social Behavior. Britni Curtis, Noelle Liberato, Megan Rulien, Kelly Morrisroe, Caroline Kenney, Vernon Yutuc, Clayton Ferrier, C. Nathan Marti, Dorothy Mandell, Thomas M. Burbacher, Gene P. Sackett and Laura Hewitson. Environmental Health Perspectives, Feb 18, 2015; doi:10.1289/ehp.1408257.
Once the embargo lifts, this article can be downloaded for free at http://ehp.niehs.nih.gov/1408257.
This study was supported by The Ted Lindsay Foundation, SafeMinds, National Autism Association, the Vernick family, and the Johnson family. This work was also supported by WaNPRC Core Grant RR00166 and CHDD Core Grant HD02274.
About The Johnson Center
The mission of The Johnson Center for Child Health and Development is to advance the understanding of childhood development through clinical care, research, and education.
